회전기계의 결함발생은 기계의 여러 상태변화에 의한 결과이며, 이 때 발생하는 증상(현상) 또한 다양하고 복잡하기 때문에 기계의 특성을 파악하고 원인을 추정하기 위해서는 매우 전문적인 지식과 오랜 경험이 필요하다. 실제 산업현장에서 사용되는 각종 회전기계들은 고성능화, 복잡화 및 전문가의 부족으로 인해, 결함발생 시 원인과 발생현상의 관계를 명확히 표현하기에는 어려움이 있다. 이에 최근에는 진단에 관한 전문적인 지식을 구조적으로 표현할 수 있는 전문가 시스템(expert system)의 도입을 위한 연구가 활발히 이루어지고 있다.(중략)

The diesel engines was invented a little more than one hundred years ago and has ever since been developed for better fuel economy, increased power and smaller size. Thanks to its fuel economy, the diesel engine is today the dominating prime mover in many applications, such as smaller power plants, commercial ships, trains, trucks, buses and all kinds of mobile construction machinery. As engine for passenger cars, the diesel engine is steadily increasing its share of the market. However, its versatility and, consequently, large prevalence have led to environmental demands to its exhaust emissions, noise and vibration. This paper deals with the noise aspects of diesel engine designs of the so-called low speed two-stroke type installed in most large ships.

Curved beams are one of the most important basic structural units as well as the beams, columns and plates. Most complicated structures consist of only these basic units and therefore it is very attractive research subject to analysis both the static and dynamic behavior of such units including the arches. The problems of free vibrations of curved beams have been the subject of much work due to their many practical applications.(an ellipsis)

The parameter modification of the initial FEM model to match it with the experimental results needs the modal information and the modal sensitivity matrix to the parameter change. There are two cases this methodology is ill-equip to deal with; the deficiency of the necessary modal information and the ill-conditioning of the sensitivity matrix. In this research, a novel concept of the feedback exciter that uses the summation of the white noise and the signals from the measurement sensors multiplied with feedback gains as the reference signal is proposed. There are 2 advantages using this external feedback excitation. First, we can use the change of the system response such as modal data by the active energy Path from the sensor to the exciter. This change of the system response can be additional clues to the system dynamics that we want to know. Secondly, the external energy Path alternates the offset of the Parameter change to the system response. That means the modal sensitivity of the parameters becomes different from the original sensitivities by the feedback excitation. Through the feedback loop, we can change the similar modal sensitivities of some updating parameters and consequently discriminate the parameters using the closed-loop modal data. To demonstrate the discrimination performance, the parameter estimation of an indeterminate structure by use of the feedback method is introduced.

This research deals with how to select connection positions of two substructures to be synthesized. The goal of this research is to find optimal connection positions in order to maximize the fundamental natural frequency of the synthesized structure. The natural frequencies of a connected structure are obtained by modal-force equations. Optimal connection positions can be selected through optimization process. In the optimization process, the natural frequencies of a connected structure are set to object function value and connection positions become design variables. The method described above is applied to synthesis problems of plates, which is initially conducted for FE models and verified through experiments. Especially in experiments, FRE(frequency Response function)s are obtained by means of the Modal Testing technique to be used in modal-force equations for synthesizing. Once the substructures are synthesized, the Modal Testing technique is again applied to spot-welded structure using the result from the optimization procedure. It is found that the fundamental natural frequency of the synthesized structure with the optimized result gives higher value than those with the initially given connection positions.

Even though embossing is an effective SDM(Structural Dynamics Modification) technique, it is difficult to implement the method in fields owing to its geometric complexity. In this research low flat-top emboss shape, rather than general shape, is considered and a systematic procedure is derived in describing the emboss implementation procedure utilizing the fact that the emboss shape can be fully expressed only if the boundary elements are appropriately given. Best position to maximize natural frequencies is found using the procedure and usefulness of the suggested technique is illustrated.

SDM (Structural Dynamics Modification) is a tool to improve dynamic characteristics of a structure, more specifically of a base structure, by adding or deleting auxiliary (modifying) structures. In this paper, the goal of the optimal SDM is set to maximize the natural frequency of a base plate structure by attaching serially-connected beam stiffeners. The design variables are chosen as positions of the attaching beam stiffeners, where the number of stiffeners is considered as a design space. The problem of non-matching interface nodes between the base plate and beam stiffeners is solved by using localized Lagrange multipliers, which act to glue the two structures with non-matching interface nodes. As fer the cases of non-matching interface nodes problem, the governing equation of motion of a structure can be considered from the viewpoint of a topological modification, which involves the change of the number of structural members and DOFs. Consequently, the eigenpairs of the beam-stiffened plate structure are obtained by using an eigen reanalysis technique of topological modifications. Evolution Strategies (ES), which is a probabilistic population-based optimization technique that mimics the principles from biological evolution in nature, is utilized as a mean for the optimization.

Nuclear fuel with a big slenderness ratio is susceptible to flow-induced vibration under very severe conditions of high temperature, high flow and exposure to irradiation in nuclear reactor. The fuel assembly should, therefore, be designed to escape any resonance due to the vibration during the reactor operation, in particular, in case of the design changes. In addition, the amplitudes due to the grid vibration, the fuel rod vibration and the fuel assembly vibration should be minimized to reduce the grid-to-rod fretting wear. Fuel assembly vibration tests in air at room temperature and in water at high temperature have been performed to investigate fuel vibration behaviors. The frequency and damping during the test in air have been compared to those in water. Through the hydraulic test, the advanced assembly has been evaluated not to be susceptible to any resonance. In addition, the test data from the tests can be used to make fuel model and to evaluate grid-to-rod fretting wear.

This paper presents an efficient dynamic modeling method for open cracked rotor-bearing systems. An equivalent bending spring model is introduced to represent the structural weakening effect in the presence of cracks. The proposed modeling method is validated through a series of simulations and experiments. First, the proposed method is rigorously compared with a commercial finite element code. Then, an experiment is performed to validate the proposed modeling method. Finally, a numerical example is introduced to demonstrate the possible application of the proposed method in the crack diagnosis fur rotor systems.

As the rotating speed of rotors is increased, the instability and power loss become serious problems. Gas bearings are introduced as a good solution to those problems. But in the development of gas bearings, high load capacity and high damping force to vibrations are required. In this study a new air bearing using leaf spring pad is introduced to improve load capacity and damping force. The experimental results of the leaf spring pad air bearings show high load capacity and high damping forces. And the results show that leaf spring pad air bearings can be simultaneously acted as radial and thrust bearings

In order to improve the instability of a plane journal bearing, the leaf spring dampers (LSD) are introduced. The effects of LSD on the stability of a plane journal bearing are investigated theoretically. The stability of a plane journal bearing with LSD are compared with the results of a plane journal bearing without LSD. And the effects of the asymmetry of the stiffness of the leaf spring damper on the stability of rotors are also investigated.

This research is to investigate the performance of a flexible matrix composite driveshaft with respect to shaft design parameters such as the number of layers, ply orientations, and material properties. A finite element formulation is utilized to estimate the allowable misalignment under given driving torque, the maximum temperature at steady states, and external damping for ensuring whirling stability under supercritical speed. Results indicate that the system performance can be greatly affected by the shaft laminate parameters, especially the ply orientations. Several sets of shaft parameters that will provide satisfactory overall system performance are derived.

In this paper, the experimental design of an intake system was studied using the two microphones method and the taguchi method. The transmission loss was utilized to represent the performance of noise reduction for the intake system which was estimated by measuring sound power at inlet and outlet with two microphones, respectively. Two microphones method used in this paper was followed by wave decomposition theory The robust designing parameters of an intake system were extracted by adapting a cost function with the taguchi method, which optimized the process. Finally the effectiveness of the propose method was validated with the experimental data.

NVH issue at idle condition is one of the major concerns of Passenger and Commercial Vehicle including Sports Utility Vehicle Especially steering wheel vibration at idle condition is a very complex problem and affected by firing frequency of the engine, stiffness of a steering wheel system and the body to which the steering wheel system is attached. To avoid vibration mode coupling between each system of a vehicle, experimental and analytical method has been used at the pre-prototype stage. The resonance frequency of the body and the frame has been decoupled by CAE and the resonance frequency of steering wheel system has been set in between the 1st bending frequency of body and frame. These Results has been used as design guidelines tot the prototype drawing stage. The experimental verification of tile modified pre-prototype vehicle shows good results of the vibration mode decouple. Modal test of prototype vehicle also confirms the vibration mode decouple between each system.

The identification of location and strength distribution of extended noise sources is important in the practical noise control engineering, especially in the viewpoint of dealing with the inherent nature of noise problem in question. For noise source ranking inside an automotive vehicle, the window method has been mainly used due to its simplicity. However, time and cost drawbacks in the measurement and inaccuracy due to low-frequency tunneling and lack of phase information have been a serious problem in using this method. In this study, the inverse FRF method was employed to carry out the noise source ranking inside an automotive vehicle and it was also used to predict the interior sound pressure with the change of sound insulation materials. As a result, it was found that the source contribution of vehicle panels could be successfully identified in comparison with the window method. The sound pressure at driver's ear position was predicted based on the obtained data and was compared with the measured data. The agreement in spectral trends was acceptable and their difference in level was within 3㏈ above 500㎐.

This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using flexible muitibody dynamic analysis and finite element one. This method is executed in 3 steps. In the la step, time dependent quantities such as dynamic loads, modal coordinates ana gross body motion of the flexible body are calculated efficiently through flexible multibody dynamic analysis. And frequency response functions are computed using Fourier transforms of those time dependent quantities. In the 2$\^$nd/ step, acoustic pressure coefficients are obtained through structure-acoustic coupling analysis by finite element analysis. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

This paper is concerned with the eddy current damper which can be used to enhance the damping of the host structure. The operating principle of the eddy current damper is first explained in detail. The dynamic interaction between the magnets and the copper plate produces eddy current thus resulting in the damping force. By attaching the eddy current damper to the host structure, the damping of the total structure can be increased so that vibrations can be suppressed. The advantage of the eddy current damper is that it doesn't require any electronic devices and power supply. The effect of the eddy current damper on the global dynamic characteristics of the structure is investigated by considering the cantilever with the eddy current damper. Experimental results show that the eddy current damper is an effective device for vibration suppression.

This paper is concerned with the experiment of vibration isolation device whit can cope with heave, pitch and roll type vibrations. This new device consists of S-shaped piezoceramic actuators supporting each corner of the plate. Small piezoceramic sensors are located at the middle of each side. This paper also presents the development and the movement of the system. The active control technique was also developed to cope with base excitation. Experimental results show that vibrations can be reduced by the new device in the case of base excitation of harmonic type.

This paper is concerned with the digital implementation of the active vibration suppression controller. The digital controllers are often implemented on the DSP board, which is very fast but expensive. There are many low-cost micro-controllers in the market but the feasibility of such micro-controllers for the active vibration suppression has never been conducted. In this study, we selected PIC 16F877 as a proper micro-controller for the digital implementation of the PPF controller. The circuit diagrams are explained in detail. Experimental results show that the low-cost micro-controller can be used as the active vibration controller.

Many researchers have tried to develop the piezoelectric shell element and verified them with the benchmarking problem of the piezoelectric bimorph beam since there is no experimental result for the control of shell structure with piezoelectric sensor/actuator. In this paper, the experiments are designed and performed to verify the control Performance of piezoelectric sensor/actuator on the shell structure. PVDF is easy to be attached on the surface of a shell structure but makes weak control forces. On the contrary, PZT makes control forces large enough to control the structure, but it is not easy to make a PZT element with curvature. To use PVDF as an actuator, the structure should be designed as flexible as possible and the voltage amplifier could make high control voltage. PVDF actuator powered by a voltage amplifier that generates output voltage from -200 to +200 volts, shows little control performance to control the vibration of an arch type shell structure. The performance of sensor looks good and the negative velocity feedback control works perfectly. The actuator voltage seems to be too small to verify the control effect Quantitatively. An experiment with high voltage amplifier is scheduled to verify the control effect Quantitatively.

This Paper presents a robust design of an Electrorheological(ER) damper using Taguchi method. Taguchi method is a robust design method that determines control parameters in the presence of noise effect. Electrode length, electrode gap, base oil viscosity and the weight ratio of ER particles are chosen for the control parameters and the temperature is considered to be a noise factor. The sensitivity of each factor with signal-to-noise(S/N) ratio and analysis of variance are investigated. The analysis results show that the electrode length and base oil viscosity of the ER fluid mostly affect the damping force in the absence of electric field. On the other hand, when the voltage is applied to the ER damper, the electrode length and the weight ratio of ER fluid exhibit significant effect. Based on the Taguchi method, an optimal configuration was designed and the robustness of the designed ER damper was validated by comparing the analysis and experimental results.

This paper is to experimentally investigate the effect of the through-flow on the absorption performance of a perforated plate system. The experiment is performed through the systematic change of the through-flow velocity, incident sound pressure level, and the geometrical parameters such as the porosity and hole diameter. From the experimental results, it is found that fur the nonlinear relationship between the acoustic resistance and incident sound pressure level there is no influence of the through-flow on the absorption performance, but for the linear relationship between them there is a strong dependence of the absorption performance on the through-flow velocity. It is also shown that the absorption performance is controllable by changing the porosity and hole-diameter in size.

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube. The pressure amplitudes and directivities of the impulse wave propagating from the exit of perforated pipe with several different configurations are measured and analyzed fur the range of the incident shock wave Mach number between 1.02 and 1.2. In the experiments, the impulse waves are visualized by a Schlieren optical system for the purpose of investigating their propagation pattern. The results obtained show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the all directions, indicating that the directivity pattern is almost same regardless of the pipe type. Moreover, it is shown that for the far sound field the perforated pipe has little performance to suppress the impulse noise.

Comparisons of measuring apparatus for sound insulation are made between a reverberation chamber and a simplified test apparatus(APAMAT II) that is used to measure sound insulation performance of inner panels for automobiles. Also, theoretical prediction by using sandwich model are made in order to compare it with experiments and to consequently provide a design tool. Comparative results show that steel ball excitation in APAMAT II has a serious problem with sound insulation performance at the low frequency region, while speaker excitation gives a good agreements with theoretical prediction.

This paper deals with transmission loss characteristics of the panel type silencer to control low frequency noise. The panel type silencer is composed of many Helmholtz resonators by side branch. Each resonator has high transmission loss on the narrow band of its resonance frequency. Direct arrangement of the resonators increases mainly the magnitude of transmission loss. If we arrange the resonators in a row, the peak and band of transmission loss are increased. This makes the resonator array to have high transmission loss in the broader band. Using this idea, we design a silencer that has broader band characteristics and smaller volume.

In this study, several methods for measuring floor impact sound were introduced. Among them, the simple methods (impedance method and diffuse index method) which can be easily applied to site works were investigated. Moreover, the comparison between the calculation results using diffuse index method and the experimental results measured in real apartment structures was conducted. Consequently, the modified diffuse index method, which can be practically used for predicting the performance of to the floor impact sound of apartment structures and can meet the allowable tolerance of Grade I (${\pm}$5㏈), was proposed.

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

철골조 초고층아파트 내부의 스포츠 시설 운영시 이를 사용하는 시설의 종류와 운동양상에 따라 아파트 상하부층에 소음진동의 민원문제를 유발하게 된다. 초고층 아파트 내부에 스포츠 시설의 배치는 이를 이용하는 사용자에게 편리성의 주지만 철골조의 특성상 충격성 진동원이 발생하는 스포츠 시설은 상하부층인 아파트에 소음진동의 연향으로 인해 이를 방지하는 설계가 요구된다. 일반적인 아파트의 충간 소음진동문제는 이를 발생시키는 상부거주자의 예절과 충간 소음진동 저감기술이지만 아파트 내부의 동일층을 경계로 위치한 스포츠 시설은 시설의 사용성에 반해 하부층에 미치는 영향을 기술적으로 저감하여야 한다. 입주한 초고층아파트에 발생하는 소음진동문제를 풀기 위하여 스포츠 시설 하부층 아파트의 소음진동 기준을 선정하고 스포츠 시설의 주된 진동원인 런닝머신의 하중식을 산정하고 충간 소음진동 저감을 위한 대책을 제시하였다.

The purpose of this study was to investigate the effect of background noise on loudness magnitude estimation of Heavy-weight impact noise. Relationship between loudness magnitude estimation and estimation methods about floor impact noise had appeared low in apartment which receive much effect of background noise. Then, to need new estimation method abut effect of background noise. Masking effects by background noise is increased steadily, there is a continuous transition between an audible impact noise and one that is totally masked. Result 1 hat analyze interrelationship of phychoacoustical data and values through Zwicker Parameters, to Investigate that an estimation experiment about Annoyance need.

The purpose of this study is to review the use of a new standard impactor, the impact ball, in evaluating heavy-weight impact noises in reinforced concrete structures. A survey revealed that children running and jumping are the major heavy-weight impact sources in multi-story residential buildings. The noise from the impact ball was measured and psychoacoustically assessed. The relationship between the noise levels and the subjective responses was also investigated. Results showed that the noise from the impact ball is similar to the noise of children running and jumping. It was also found that the noise level of the impact ball is slightly higher than the noise level of a bang machine, although the impact ball has a lower impact force.

Noise barrier is used for noise reduction method of traffic noise. The length and the total cost of that are increased in this national area. But, a maintenance management of noise barrier is not systematic, and the guideline of that is not prepared for maintenance mannual. The situations of existed installation and management of noise barriers installed at 3,619 positions were investigated by questionnarie and direct field survey. And comparisons with foreign management guideline of noise barrier were carried out. The results show that the improvement methods of maintenance management system such as practical checklist and required items for management of noise barrier were suggested.

For the noise reduction measures in a construction field or near the traffic line receiver is often the most economic measure in order to exclude the propagated sound. The dimension of the barrier is decided by the noise and construction design, and the constructive quality of a soundproof panel shall be secured in accordance with KS F4770 to guarantee the safety of sound barriers. In this paper the problems included in the KS F4770-1 that is the regulation for the metallic sound barrier of the absorption type are identified and it is suggested what to be corrected or improved. Through a series of the analyses, conclusions were reached that it is required to improve test methods in KS F4770-1 as well as to break down test loads for building more cost-effective sound barrier.

A new analytic method is presented for predicting the performance of noise barriers having complicated end shapes like "Y", "T", inverted L, and other shapes. The insertion loss of the barrier is predicted by summation of multiple diffractions occurring at the comer points. Although previous studies treated diffractions occurring only at the convex points, the method presented in this paper considers diffractions at the concave point. As numerical examples, a partially inclined noise barrier and "T" shape noise barrier are studied. It is shown that the diffraction at the concave point may be neglected if the shortest path does not include the concave comer point.

The soundproof barrier used to reduce the traffic and rail noise is usually designed to the point of view of the acoustic performance such as absorption ratio and transmission loss. But, because the surface of soundproof barrier is polluted by the air pollutant or discharge gas of automobiles, so it's surface cleary maintained by the periodic washing with detergent. But in this case the environmental pollution and the working expenses are worried. So, the objective of this study is to develope the soundproof panel with the self-cleaning properties only by raining.

This study aims to investigate dynamic properties of express buses in the very low frequencies which affect motion sickness incidence. Since passengers often use express buses for long distance traveling, it is a critical point whether a give rise to motion sickness or not. In the study accelerations at the three points on the floor of the six test vehicles were measured during the driving at constant speeds. By applying frequency weighting curves suggested in ISO 2631-1 and ISO 2631-3, physical amount of accelerations were changed into perceptual amount which determines incidence of motion sickness. Motion sickness dose values were calculated from the frequency weighted time history of accelerations, and compared between the vehicles, driving conditions, and the seat positions in the bus. During the driving on public road and high ways for 50 minutes vomiting incidence ratios ranged 0.4 to 0.8%, which were equivalent to 2.4 to 4.8% for 5 hours' driving. The value of 4.8 % means two among 45 passengers may vomit after the traveling, which is very serious situation. Considering the very smooth driving condition at which the data were collected, motion sickness dose values will increase in real situations

When considering the effects of whole-body vertical vibration, it is valuable to have an understanding of the mechanical characteristics (mechanical impedance and apparent mass) of the body. This paper addresses experimental results carried out to investigate the characteristics of apparent masses fer 41 Korean. The apparent masses of the seated human body in vertical direction were measured during different experimental conditions, such as vibration excitation level (0.5-2 ms$\^$-2/ r.m.s). frequency range (1-50Hz), and upper body posture (relaxed, normal and backrest-upright). We showed the average of all subjects and all conditions and compared the results with ISO5982/DIS (2000).

This paper introduces attempts to obtain the 'representative' characteristics of the mechanical impedance of seated Korean subjects under vertical vibration. Individual responses of driving-point mechanical impedance obtained from forty-one Korean subjects are illustrated. Four kinds of vibration levels and three different sitting postures are selected to collect the responses of each subject. Those individual responses are used to estimate the 'mean' mechanical impedance, which may be expected to be a representative model to Korean subjects. Several interesting features of the estimated mechanical impedance are suggested and compared to those of ISO/DIS 5982.

The regulation for floor impact sound level is expected to be amended to 50㏈(L$\_$i, Fmax, AW/) and below in heavy-weight impact sound and 58㏈(L'$\_$n, AW/) and below in light-weight impact sound in Korea. The purpose of this paper is to analyze the influence factors of floor impact sound levels in apartments. The influence factors were air pressure of bang machine, height of microphones, data acquisition rate, etc. The air pressure range of bang machine were from 2.2 Pa to 2.6 Fa. Five microphones were installed at a height of 0.5m, 0.7m, 0.9m, 1.2m, 1.5m or 1.7m from floor level. The floor impact sound level was varied about 1-3㏈(L$\_$i, Fmax, AW/) in heavy-weight impact sound according to the influence factors.

This paper presents a result of performance evaluation fur non-contact scanning probe microscopy with respect to the vibration characteristics of cantilevers with tips. One of the current issues of the scanning probe microscopy technology is to increase the measurement speed, which is closely tied with the dynamic characteristics of cantilevers. The primary concern in this research is to investigate the relation between the maximum possible speed of non-contact scanning probe microscopy and the dynamic characteristics of cantilevers. First, the finite element analysis is made fur the vibration characteristics of various cantilevers in use. The computed natural frequencies of the cantilevers are in good agreement with measured ones. Then, each cantilever is tested with topographic measurement for a standard sample with the scanning speed changed. The performances of cantilevers are analyzed along with the natural frequencies of cantilevers. Experiments are also performed to test the effects of how to attach cantilevers in the piezo-electric actuator. Finally, measurement sensitivity has been analyzed to enhance the performance of scanning probe microscopy.

Vibration table is required to obtain high packing density in expendable pattern casting process. Packing density, which is an important manufacture factor, depends on the vibration pattern induced by vibration table. Modal test is utilized to identify the dynamic characteristics of vibration table. And finite element method is used to modify flask by fixing the stiffener. The positions of stiffener to modify are found and the natural frequency could be easily shifted to the objective value by using sensitivity analysis.

This paper discusses on the dynamic responsed of an elastically restrained beam under a moving mass of constant velocity. Governing equations of motion taking into account of all inertia effects of the moving mass were derived by Galerkin's mode summation method, and Runge-Kutta integration method was applied to solve the differential equations. Numerical solutions for dynamic deflections of beams were obtained for the changes of the various parameters (spring stiffness, spring position, mass ratios and velocity ratios of the moving mass). In order to verify the numerical predictions for the dynamic response of the beam, experiments were conducted. Numerical solutions for the dynamic responses of the test beam have a good agreement with experimental ones.

A Suspension system of a car is composed of dampers and springs. The dampers and springs usually have nonlinear characteristics. However, the nonlinear characteristics of the springs and dampers through analytical model cannot agree with the experimental results. Therefore, the nonlinearity of the suing and damper should be known from the experimental results. In this study, the methods of system identification for nonlinear dynamic system in time domain are discussed and the nonlinear parameter estimation lot experimental data of an EF-SONATA car was done. The results show that a cubic and a coupled term should be considered to model the suspension system.

We investigate global bifurcation in the motion of an harmonically excited circular plate with one-to-one internal resonance. A perturbation method developed by Kovacic and Wiggins is used. Silnikov type homoclinic orbit has been pursued but it has turned out not to exist.

To ensure a safe operation of the prototype KGT-74 ㎾ small gas turbine, vibrational reliabilities of the compressor 1st, 2nd. and 3rd stages and turbine blades have been estimated and reviewed. FE analyses have been tarried out to obtain the natural vibration characteristics of the blades, and impact modal testings have been performed on every each one of the blades to measure their 1st natural frequencies. Then, the Campbell diagram analyses have been carried out to Judge the safety of the blades from resonant failures up to 6k harmonics. Results show that the compressor 1st stage blade is exposed to a potential resonant failure with 3k harmonic around a rated speed of 30,000rpm but that the other compressor 2nd and 3rd stages and turbine blades are safe from resonant failures. Finally. 27,900 rpm Is selected as the safe operation limit for the KGT-74 ㎾ gas turbine relative to the blade vibrations.

This paper suggests a fuzzy expert system for fault diagnosis of rotating machinery, based on modulated databases. In the proposed system, alarm and trip levels are set based on ISO, considering operating condition, machinery type and maintenance history. Input signals for diagnosis, such as sub- and super-harmonic components of vibration and mean value, are normalized from 0 to 1 under the threshold level and otherwise equal to one so that chronic faults slightly below the threshold level can be monitored. The database for diagnosis consists of two modules: the well-known Sohre's chart module and if-then type rules. The Sohre's chart is utilized for the most common problems of high-speed turbomachinery, while the rule-based module, which was collected from many papers and reports, is for diagnosing peculiar faults according to the type of machinery. To infer the results from two modules, a fuzzy operation of Yager sum was adopted. Using a simulator constructed in laboratory, experimental verification was performed for the cases of resonance and housing looseness which were intended. The experimental results show that the proposed fuzzy expert system has feasibility in practical diagnosis of rotating machinery.

The vibration of washing machine at spinning cycle is important problem that affects the performance of a product. In this raper, the inner structure of the washing machine is modeled as a rigid body suspension system and transfer farce caused by rotating unbalance mass is obtained using Newton's the 2nd law. and this model is used to predict the verge of walking instability during the spinning cycle. The walk of the drum washing machine is suggested by calculating the force transmissibility between drum and the cabinet. As calculating the resultant force exerted for cabinet, the friction coefficient of the pad is suggested to avoid the walk. In addition, relation between translational slip and rotational slip is derived and method to avoid the rotational slip is introduced.

In general industrial rotating machinery is operated under 3,600 rpm as rotating speed and designed to have critical speed that is above operating speed. So, there was no problem to operate rotating machine under critical speed. But nowadays, they should be operated more than the frist critical speed as usual with the trend of high speed, large scale and hish precision in industries. In case of the large rotor assembly as the trend of large scale, using fitting method of disk or cylinder on shaft is rising for the convenience of assembly and cutting down of manufacturing cost. The shrink fitting is used to assemble lamination part on shaft for manufacturing of rotor of motor or generator in many cases and also is widely used for other machinery. In rotating system, which is compose of rotor and bearing, the critical speed is determined from inertia and stiffness for the rotor and bearings. In case of fitting assembly, analysis and design of the rotor is not easy because the rotor stiffness is determined depend on a lot of factors such as shaft material/dimension, disk material/dimension and assembled interference etc. Therefore designer who makes a plan for hish-speed rotating machine should design that the critical speed is located out of operating range, as dangerous factors exist in it. In order to appropriate design, an accurate estimation of stiffness and damping is very important. The stiffness variation depend on fitting interference is a factor that changes critical speed and if it's possible to estimate it, that Is very useful to design rotor-bearing system. In this paper, the natural frequency variation of the rotor depends on fitting interference between basic shaft and cylinder is examined by experimentation. From the result, their correlation is evaluated quantitatively using numerical analysis that is introduced equivalent diameter end the calculation criteria is presented for designer who design fitting assembly to apply with ease for determination of appropriate interference.

Nowadays many peoples are using helicopter in various fields, not only military use but also common people applications such as air-measurement, photography, transportation of goods and persons, saving life and fire fighting etc. And it will be expected more popular than now. Most important part of helicopter to increasing performance and to reducing noise is rotor hub-system. Hub system consists of rotor-blade and rotor-hub. We participate to develop next-generation rotor hub system with elastomeric bearing, part of rotor hub. In this paper we introduce about the role and shape of elastomeric bearing in next-generation helicopter hub system. Then we study about bearing-material requirements and measuring methods. Finally we represent some experimental results.

Analysis and experiment on dynamic characteristics of automotive roof have been carried out experimentally and numerically to design a lightweight roof. Finite element analysis of a conventional steel automotive roof was verified by experiments on vibration characteristics. The dynamic analysis of carbon fiber reinforced composite automotive roof shows that the roof stiffness changes as the fiber orientation of the laminated panel changes. Optimization results yielded a composite roof, which was 52% lighter, than the steel conventional steel automotive roof. This paper addresses a design strategy of composite roof for weight reduction.

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

Acoustic holography is adopted in identifying the noise sources of a vehicle's underbody. Wind noise from a vehicle's underbody accounts for a large portion of the overall noise level due to the complex flow structure. Current study presents the development process of acoustic holography in the vehicle underbody, and discusses the results obtained using the method. Difficulties associated with using acoustic holography as well as the implication of the results regarding future noise reduction possibilities are discussed.

According to the remarkable reduction of the vehicle noise, the important of tire noise which is generated from the vehicle and the necessities of the researches for the noise reduction are emphasized. In this study, we have studied the road noise which is excited by the interaction between tire and road. In order to evaluate the road noise, we carry out the subjective test(feeling test). In order to consider the effect of the vehicle suspension for the tire/road noise, we are equipped with identical tires on the differential vehicle suspension and evaluate the road noise. In order to consider the effect of the tire structure for the tire/road noise, we evaluate the some tires with various structures. From the test results, we fine that the difference of road noise is generated by the variation of the vehicle suspension. Also, we can select the optimized tire structure which can be reduced the road noise.

A new mechanical-electrical hybrid passive dam ping treatment is proposed to improve the performance of structural vibration control. The proposed hybrid passive damping system consists of a constrained layer damping treatment and a shunt circuit. In a passive mechanical constrained layer damping, a viscoelastic material damping layer is used to control the structural vibration modes in high frequency range. The passive electrical damping is designed for targeting the vibration amplitude in the low frequency range. The governing equations of motion are derived through the Hamilton's principle. The obtained mathematical model is validated experimentally. The presented theoretical and experimental techniques provide invaluable tools for controlling the multiple modes of a vibrating structure over a wide frequency band.

This paper presents a study of low frequencies volume velocity vibration control of a smart panel in order to reduce sound transmission. A distributed piezoelectric quadratically shaped polyvinylidene fluoride (PVDF) polymer film is used as a uniform force actuator and an array of 4$\times$4 accelerometer is used as a volume velocity sensor for the implementation of a single-input single-output con rot system. The theoretical and experimental study of sensor-actuator frequency response function sho vs that this sensor-actuator arrangement provides a required strictly positive real frequency response function below about 900Hz. Direct velocity feedback could therefore be implemented with a limited gain which gives reductions of about 15㏈ in vibration level and about 8 ㏈ in acoustic power level at the (1, 1) mode of the smart Panel. It has been also shown that the shaping error of PVDF actuator could limit he stability and performance of the control system.

This paper presents investigation of damping characteristics of squeeze mode type MR (Magneto-Rheological) mount experimentally. Since damping property of the MR fluid is changed by variation of the applied magnetic field strength, squeeze mode type MR mount proposed in the study has variable damping characteristics according to the applied magnetic field s strength. In the present work, the performance of the mount was experimentally investigated according to the magnetic field strength and exciting frequencies. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents in this study and MR effect is reduced by increasing exciting frequency.

천공요소는 자동차의 배기 소음기, 공조기의 소음기 등을 포함하는 다양한 소음계에 널리 사용된다. 일반적으로 천공요소 들은 평균 유동과 소음원이 동시에 존재하는 환경에서 사용되며, 평균 유동 및 관 내부의 음압 레벨의 변화가 천공 부근에서의 임피던스에 큰 영향을 미치게 된다. 천공요소의 임피던스의 변화는 소음기의 음향학적 특성에 영향을 미치게 되므로, 유동이나 음압 조건이 임피던스에 미치는 영향에 대한 연구가 중요하다. 본 연구에서는 정밀 계측 및 전산유체역학적 모형을 이용해 천공요소의 임피던스에 영향을 미치는 주요 세 가지 인자 - 스치는 유동, 통과하는 유동, 음압 레벨 - 들을 고려하여 임피던스를 분석하고, 그 상관관계를 밝혔다.

This paper deals with transmission loss of 3-dimensional rectangular plenum lined chamber. There are three kinds of rectangular plenum lined chamber: throughflow type, flow-reversal type, and end-in/side-out type. The combination of above three types of rectangular plenum lined chamber is used for the commercial HVAC system and automobile exhaust system. However, the ambiguity and complexity of sound absorbing material property and 3-dimensional property have impeded research. In this paper, the transmission loss of three kinds of rectangular plenum lined chamber is derived and calculated. The effect of increase of sound absorbing material is also considered. Analytical solution is calculated by using the locally-reacting property of sound absorbing material.

This study is put a focus on the identification of sound characteristics according to the interior configuration of sound absorption material and air gap. Noise barrier is general consists of front perforated panel, air layer, sound absorption material, air gap and back plate. Noise barrier is required to the NRC value of 0.7. The absorbing performance of the noise barrier relies on the opening ratio of the perforated panel and the efficiency of the absorbing material. This study has observed the effect of opening ratio and hole size, the increase of sound absorbing performance by the configurations of sound absorption material and air gap. New designed noise barrier is achieved the acoustical performance of 0.87 the measurement in a reveration room.

Conventional method for designing and installing anechoic chambers is to utilize porous wedges for the sound absorbers. As cutoff frequency lowers down such as 63Hz or 50Hz, the corresponding long wedges diminish the free field area of the chamber. In this study, a new broadband compact absorber(BCA) is introduced which absorbs acoustic energy down to 50Hz. Most prominent is that it measures only 250mm thick. A freely vibrating panel between the non-fibrous absorbers allows tuned absorption at the low frequency region in addition to the high frequency absorption resulted from the conventional absorber installed at the front. Standing waves at low frequency range are suppressed as the BCA modules which are tuned to the corresponding modes absorb sound energy effectively, resulting in anechoic condition. Not only the low frequency performances, but the high frequency absorption is measured to meet adequate conditions for the anechoic chamber. Realized BCA chambers are presented.

The FM demodulation method for a bulk homodyne laser interferometer is presented. The Doppler frequency that represents the surface velocity of a vibrating object is obtained by using the bulk homodyne laser interferometer, and converted to the voltage signal by using the proposed analogue FM demodulation circuit. The DC offsets of the interferent signals that are obtained from the bulk homodyne interferometer are eliminated by using a simple subtraction. The new method for compensation of the asymmetry of each channels is presented. The light power variation of the interferometer is normalized by using the Auto Gain Controller(AGC). The proposed FM demodulation algorithm is proved by the theoretical method, and validated by the experimental results. In experiments, the proposed FM demodulation algorithm is compared with the conventional demodulation methods.

This paper studies the error of pressure, particle velocity, and intensity which are distributed in a space. Errors may be amplified when other sound field variables are predicted. We theoretically derive their bias error and random error. The analysis shows that many samples do not always guarantee good results. Random error of the velocity and intensity are increased when many samples are used. The characteristics of the amplification of the random error are analyzed in terms of the sample spacing. The amplification was found to be related to the spatial differential of random noise. The numerical simulations are performed to verify theoretical results.

The frequency response function(FRF) of each substructure is used for the transfer function synthesis method(TFS). The dynamic characteristics of the full system are obtained by synthesizing FRFs of each substructure. The validation of TFS depends on accuracy for FRF of each substructure. Impact hammer testing Is widely used to obtain the modal characteristics of structures However. the FRF obtained from impact hammer testing contains bias errors, such as finite record length error and leakage error of which characteristic depends on data acquisition time which we call record length. In this paper, a method to remove hose errors is proposed so as to enhance results of TFS. Numerical and experimental examples show that the FRF of full structure can be predicted nearly exactly by the method proposed in this paper.

There are some methods fur extracting mode shapes from a continuously scanned data such as a modulation, Chebyshev polynomial, and Hilbert approach. In this paper, Chebyshev and Hilbert approaches were investigated through the numerical experiment first. As some experimental parameters were altered with small quantities, data were checked and plotted. From those results, the effects of unexpected parameters will be configured. And then, it will be actually helpful to select the proper method for specific testing environments.

This paper addresses the results of experimental and analytical study on the effects of dynamic interaction between vehicle and bridge on modal properties of bridge. Based on ambient vibration test and vehicle impact test on a bridge, it is found that the natural frequencies of bridge are varied by vehicle passing. Analytical studies for the effects of vehicle position, speed, damping, mass ratio and frequency ratio on bridge-vehicle interaction are carried out using complex eigenvalue analysis and numerical integration in time domain. The results show that vehicle properties except speed cause significant change of natural frequency as well as damping of bridge.

As a critical member of cable-stayed bridges, stay cables play an important role of supporting the entire structure. Traffic, wind or rain-wind induced vibrations of stay cables would be a major cause of degrading both safety and serviceability of the bridge. One of the effective alternatives to solve this problem is to employ the cable dampers. In order to design the cable damper optimally. it is necessary to exactly estimate the dynamic characteristics of the existing cables. Therefore, in this study, a cable exciting system (exciter) controlled digitally was developed. And to evaluate the performance of the cable exciter developed, a solution of the differential equation of cable motion considering the exciter was derived. Using the cable exciter. sine sweeping and resonance tests on a cable model were carried out to obtain the dynamic characteristics effectively.

This paper presents a system identification (SI) scheme in time domain using measured acceleration data. The error function is defined as the time integral of the least square errors between the measured acceleration and the calculated acceleration by a mathematical model. Damping parameters as well as stiffness properties of a structure are considered as system parameters. The structural damping is modeled by the Rayleigh damping in SI. The regularization technique is applied to alleviate the ill-posed characteristics of inverse problems. The validity of the proposed method is demonstrated by an experimental study on a shear building model.

This paper presents a generator for stand-alone vibration monitoring system of bridge structure based on ambient vibration of bridge. In this paper, a novel electric power generator which has minimum effect of armature reaction is proposed. The related mechanical and electrical design equations are obtained and a pilot generator has been implemented. In addition, the charging system for extremely low generator current is discussed, and some improvements are identified for the system. This investigation reveals that diode characteristics of rectifier is dominant factor in the charging process. Finally, both the simulation, which uses real measurement data of the Namhae bridge as input of the pilot generator, and indoor test are carried out. The results showed the applicability and effectiveness of the stand-alone vibration powered generator.

This study presents a new analysis of blast vibration equations of a bridge structures using a reliability index. Changing the reliability makes each blast vibration equation. The blast equations are divided into three classes, having 50%, 90% and 99.9% at ${\beta}$=0, 1.28 and 3 respectively. In the result of this research, the assumption equations which used ${\beta}$=1.28 is suitable. By using these blast equations, it is possible for users to predict reliable ground vibration values upon demand.

Natural periods are usually determined by the so-called linearized finite displacement theory even for a suspension bridge. This linearized method, with formulating structural stiffness by taking dead-load tension into consideration, calculates the natural periods of the bridge. As a result, the assumed initial tensions for each cable member may affect the accuracy of calculated natural periods and some other dynamic responses. This paper mainly demonstrates the effect of initially introduced tension accuracy on the evaluation of dynamic characteristics for a suspension bridge.

Effect of hand-transmitted vibration on human discomfort and health was reviewed. Since the effect by hand tool was more serious than those by any other vibration environments, western countries have protected hand tool workers by regulations. International organization for standardization legislate standard, ISO 5349, at 1979 for the measurement and evaluation of the effect. Afterwards, more than twenty standards on hand-arm vibration were enacted to protect any damage of hand tool users. Even though Korea Standards adopted ISO 5349 in 2001, it is required an action plan should be applied to all of work environments, especially to the workers using pneumatic tool workers such as miners, construction workers, and etc.

선박에 탑재되는 기기나 장비는 선박으로부터 받게 되는 진동환경에서 성능이 지속적으로 유지되어야 하므로 이에 대한 내구성능이 요구된다. 일찍이 미국 해군에서는 함정 탑재기기의 환경진동시험에 관하여 MIL-STD-167-1$^{(3)}$ 에 규정하고 이에 따라 환경진동에 대한 내구성능 입증을 요구하고 있다. 우리나라 해군도 이 표준을 그대로 적용하여 시행하고 있다. 반면에, 일반선박의 경우에는 함정에서와 같이 엄격하게 탑재기기의 진동 내구성능시험을 요구/시행되고 있지 않다. 1996년에 국제표준화기구(중략)

This part of ISO 1940 covers the following: a) identification of errors in the balancing process of rigid rotors: b) assessment of errors: c) guidelines for taking into account: d) the evaluation of residual unbalance in two correction planes. Detailed consideration of errors associated with the determination of residual unbalance is covered in the first part of ISO 1940.

1. Schedule for the meetings of ISO/TC108 Mechanical vibration and shock and ISO/TC108/SC3 Use and calibration of shock measuring instruments 2. Minutes for the seventh meeting of ISO/TC108/WG23 Mechanical vibration and shock - Resilient mounting systems - Information for the application of source and receiver isolation (omitted)

A nonlinear modeling method for an axially oscillating cantilever beam with a concentrated mass is presented in this paper. Hybrid deformation variables are employed fur the modeling method with which frequency response characteristics of axially oscillating cantilever beams are investigated. The geometric nonlinear effects of stretching and curvature are considered to accurately predict the frequency response characteristics of the oscillating cantilever beam. The effects of the magnitude and the location on the concentrated mass on the frequency characteristics are investigated. It is found that the dynamic instability is significantly influenced by the two parameters.

Frictional heating in brakes causes thermoelastic distortion of the contacting bodies and hence affects the contact pressure distribution. The resulting thermo-mechanical coupling can cause thermoelastic instability (TEI) if the sliding speed is sufficiently high, leading to non-uniform heating called hot spots and low frequency vibration known as hot judder. The vibration of brakes to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness ${\alpha}$ slides with speed V between two half-planes which are rigid and non-conducting. The advantage of this properly simple model permits us to deduce analytically the critical conditions for the onset of instability, which is the relation between the critical speed and the growth rate of the interface temperature and pressure. Symmetrical component of pressure and temperature distribution at the layer interfaces can be more unstable than antisymmetrical component. As the thickness ${\alpha}$ reduces, the system becomes more apt to thermoelastic instability. Moreover, the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with low critical speed, it might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.

Vibration localization characteristics of open loop repeated structures with mistuning are investigated in this paper. Mistuning of a periodic structure often creates significant non-uniformity in vibration responses. As a result of the localization, critical fatigue problems often occur in repeated structures. Therefore, it is of great importance to predict the vibration response of the mistuned repeated structures accurately. In this paper, a simplified model for the open-loop repeated structure is introduced and dimensionless parameters which influence the localization characteristics are identified. The effects of the parameters on the localization characteristics are investigated through numerical study.

The vibration of a flexible cantilever tube with nonlinear constraints when it is subjected to flow internally with fluids is examined by experiment and theoretical analysis. These kind of studies have often been performed that finds the existence of chaotic motion. In this paper, the important parameters of the system leading to such a chaotic motion such as Young's modulus and coefficient of viscoelasticity in tube material are discussed. The parameters are investigated by means of a system identification so that comparisons are made between numerical analysis using the parameters of a handbook and the experimental results. The chaotic region led by several period-doubling bifurcations beyond the Hopf bifurcation is also re-established with phase portraits and bifurcation diagram so that one can define optimal parameters for system design.

A method of identifying structural parameters such as stiffness and damping coefficients at interfacial points of vibro-acoustic systems is suggested using an optimization technique. To identify the parameters using a numerical optimization algorithm, cost functions are defined. The cost function should be zero at the correct parameter values. To minimize the cost functions using an optimization technique, a design sensitivity analysis procedure is developed in the framework of the multi-domain FRF-based substructuring method. As a numerical example, a ladder-like structure problem is introduced. With known parameter values and different initial guesses of the parameters, convergence characteristics to the exact value are compared for the three cost functions. Investigating the contours of the cost functions, we find the first cost function has the largest convergent region to the correct value. As another practical problem, stiffnesses of engine mounts and bushings in a passenger car are identified. The numerical examples show that the proposed method is efficient and accurate even when applied to realistic problems.

The paper represents the stability of a rotor system with the squeeze film damper (SFD) using an electromagnet. The electromagnet is installed in the inner damper of the SFD. The proposed SFD has basically property of a conventional SFD and variable damping property according to variation of the applied electric current. Therefore, when the applied current controlled, the whirling vibration of the rotor system can be effectively reduced in a wide operational speed range. In the present work, the performance of the SFD was experimentally investigated according to changing the magnetic field strength. When the applied current increased, the whirling amplitude greatly reduced and the damping ratio also increased.

The aircraft engine is usually supported by rolling element bearings and has a small damping rate, which is vol y sensitive to external force. The high-performance requirement of the rotors leads to complex assembly designs and are more flexible. Squeeze film dampers (SFDs) are introduced to provide damping while crossing the critical speeds and stability to the rotor s :stem. Hence, the focus of the present investigation is on the decision of an optimal size of the flexible rotor system supported by the squeeze film dampers to minimize the maximum transmitted load and unbalance response over a range operating speeds. The enhanced genetic algorithm (EGA), which was developed by authors, is used in the optimization process. This algorithm is based on the synthesis of a modified genetic algorithm and simplex method. The results show significant benefits in using EGA when compared with nonlinear programming (NLP).

The determination of unknown parameters in rotating machinery is a difficult task and optimization techniques represent an alternative technique for parameter identification. The Simulated Annealing(SA) and Genetic Algorithm(GA) are powerful global optimization algorithm. This paper proposes new hybrid algorithm which combined GA with SA and local search algorithm for the purpose of parameter identification. Numerical examples are also presented to verify the efficiency of proposed algorithm. And, this paper presents the general methodology based on hybrid algorithm to identify unknown bearing parameters of flexible rotors using measured unbalance responses. Numerical examples are used to ilustrate the methodology used, which is then validated experimentally.

Conventional modal analysis techniques are known to be inappropriate for asymmetrical rotor systems. when the equations of motion are written in the stationary coordinates, due to the presence of time varying parameters. This paper presents a generalized modal analysis method for asymmetrical rotor systems in the stationary coordinates, employing the modulated coordinates and the lambda matrix formulation. A numerical example with a flexible asymmetric rotor model is provided to demonstrate the effectiveness of the proposed modal analysis method. As an application of the proposed method, modal analysis is also performed with an open cracked rotor system.

Vibration of rotating machinery is a factor that is something to do with abnormal machinery. Former days, Perception of vibration at rotating machinery had used Shaft rider type. Shaft rider type was adhered to surface of shaft and detected vibration of rotating machinery. Recently, Perception of vibration at rotating machinery uses to non-contact sensor. Working principle of non-contact sensor is used of eddy current. Vibration at rotating machinery appears to deviation of eddy current. In this paper, We investigate abnormal vibration due to non-contact sensor.

When a rail vehicle transverses tight curves, it often emits an intense, high-pitched squeal. This squeal has always been noticed as one of the most disturbing noise sources of railway systems. At present, w cannot predicted squeal noise that is influenced by a large number of dependent parameters. In this study, we performed structural analysis to find out the frequency of the wheel and measured squeal noise at Seoul subway. We also tested reduction effectiveness of squeal noise through rail lubricator

This paper describes an overall Noise Assurance Plan(NAP) in the project for developing a new rolling stock. In this paper, the procedure for implementing noise control activities for each development stage on the basis of the NAP is also described. The NAP was developed by KITECH(Korea Institute of Industrial Technology) and ODS(${\Phi}$degaard ＆ Danneskiold-Samsoe in DENMARK). Generally, the main objective of NAP is that noise assurance plan applies to the establishment of organization and personnel's roles and responsibilities, set-up of overall procedure and internal audit program. Here, a few comments are made to the deviations of the actual procedure(G7 Project) relative to the suggested NAP presented. The major difference between the suggested NAP and the actual procedure was the late involvement of the noise consultant resulting in suggestions for design improvements could not be implemented due to the advanced stage of the design. Similarly, the important task of preparing sub-supplier specifications was performed. The proposed NAP will be an efficient tool for noise management in the R＆D project for new rolling stock. Specially, in case that several companies and institutes are involoved in the R＆D team

Recently, the ride comfort problem becomes increasingly important because of today's needs for train speedup. The concept of ride comfort is equivocal. Generally, it is defined as the body vibration. The prototype of Korean high speed train (KHST), composed of two power cars, two motorized cars and three trailer cars, has been designed, fabricated and tested by the domestic researchers. In this paper, the ride comfort has been reviewed by the experimental method. The on-line test of KHST has been carried out up to 260km/h in the KTX line and proved that KHST has no problems from the viewpoint of the comfort ride at this speed. And the ride index lot KHST has been predicted at 300km/h and 350km/h by fitting curve.

Korean High Speed Train(KHST) has been tested on the high speed test line in Osung site of Korea High Speed Rail Construction Authority (KHRC). since it was developed as G7 Project Plan In 2002. This paper introduces the dynamic test devices in KHST and shows the comparison between the results of test and theoretical computing results which derive from the new model for KHST dynamic behavior. Previous computer simulation model for KHST was developed to review wether the vehicle system was satisfied with the dynamic performance requirements during the design procedure. But It should be applied the results of the parts test for suspension elements in order to compare between the results of computation and real test. Using VAMPIRE Program made by AEA Technology in UK. the new model also was modified. This paper shows that the static wheel loads calculated from new model is similar to test results. For test on high speed line, we prepared the test devices for evaluating the dynamic performances. which was consisted of the accelerometers( based on Kisler Co.) and the data aquisition systems (based on National instrument Co.), and test program coded by LabView 6i program. These lest devices and programs are flexible to extension the channels for adding sensors and connect to the ethernet network. The acceleration of car bodies, bogie frames and axle boxes were compared between the results of computation and test at 150km/. This paper shows that the results of test were high in high frequency band range but similar frequency band range. It might be considered that these differences were caused by the test which did not performed at constant speed for comparison analysis. Also. It will be able to understand the differences and make better results through a lot of tests planed in future.

In this paper, a numerical method for evaluating the efficiency of vibration reduction of substructure under floating slab track is developed for optimal design of floating slab track. The equation of motion for train and track interaction system is derived by applying compatibility condition at the contact points between wheels and rails. The train is modelled by 3-masses system and the track by continuous support beam system. Numerical analyses are carried out to investigate the effects of train speed, stiffness and damping of slab-pad, and track irregularity upon vibration reduction in substructure under the track.

In recent years, the demand of mobile device, such as digital camera, camcorder and PDA, increases remarkably. So, requirements of the mobile information data storage used in the mobile devices increase noticeably also. 1" micro data storage is a kind of mobile storage. which has a CF type II form factor, and the similar structure of the general 3.5" HDD. In this paper, we developed the self acting air-lubricated ceramic bearing for the 1" micro data storage. The self acting air-lubricated ceramic bearing Is superior to the fluid bearing and the ball bearing on power consumption.

This research proposes a finite element method to determine the natural vibration characteristics of the spinning disk-spindle system in a HDD including the flexibility of supporting structure. Finite element equations of each substructure are derived with the introduction of consistent variables to satisfy the geometric compatibility at the internal boundaries. The natural frequencies and modes from the global asymmetric matrix equations of motion are determined by using the implicit restarted Arnoldi iteration method. The validity of the proposed method is verified by the experimental modal testing. It also shows that the flexibility of base plate plays an important role to determine the natural frequencies of the spinning disk-spindle system in a HDD.

This paper presents a method to investigate the characteristics of a ball bearing and the dynamics of a HDD spindle system due to temperature variation. Finite element model is developed fer the rotating and stationary parts of a HDD spindle system separately to determine their thermal deformations by using ANSYS, a finite element program. Then, the relative position of the rotating part with respect to the stationary part is determined by solving the equilibrium equation of the contact force between upper and lower ball bearings. The validity of the proposed method is verified by comparing the theoretical natural frequencies of a HDD spindle system with the experimental ones before and after temperature variation. It shows that the elevated temperature results in the increase of contact angle and the decrease of bearing deformation, contact force and bearing stiffness, which result in the decrease of the natural frequencies of a HDD spindle system.

It has been widely known that geometrical or form errors of ball bearings such as ball size error, ball waviness, inner and outer race waviness due to inherent manufacturing imperfection are one of the major sources of uncontrollable non-repeatable run-out (NRRO) vibration in HDD spindle motor. NRRO in HDD is also known to be the primary cause of limiting the storage capacity of HDD. In this paper, We performed vibration analysis for NRRO a ball bearing being used in 3.5" HDD spindle motor. To theoretically estimate NRRO considering the geometrical errors of ball bearing components, a simple three degrees of freedom model was proposed and then vibration analysis for axial and radial NRRO was conducted utilizing the measured geometric imperfection of a bearing with both the waviness magnitude and phase taken into account. Effects of bearing preload and clearance on NRRO was also investigated as an effort to predict their optimum values minimizing bearing NRRO.

To solve a problem of micro drive due to small size and portability, it is necessary to understand and to investigate micro drive widely ,deeply. So, we performed modal analysis of suspension of micro drive, and load/unload experiment for Input current to VCM coil and disk speed. To determine the effect of ramp profile, curve fitting of lateral speed is performed with equation of speed. The results indicate that small load/unload speeds decrease the number of head/disk contacts, and during unloading process, low disk speed increase the number of head/disk contacts.

In order to meet the growing demands for higher storage density as well as lower noise level, the spindles In hard disk drives are to be supported by hydrodynamic bearings in place of conventional ones. However, the existing models are inappropriate to apply to accurate Prediction or vibration characteristics because the Inn spindle tends to take quite a complex shape to secure the performance of the new type bearings. In this context, this paper treats analysis of free and forced vibrations of such-designed HDD spindles based on more sophisticated models and validation by means of experiments. Remarkably, to this end each component in the system is modeled as elastic adopting the finite element method.

Recently a number of social surveys on community response to environmental noises have been conducted. Since standardized noise annoyance scales were needed to compare the results from various areas, ICBEN(International Commission on Biological of Noise) Team 6 planned a international joint study and constructed comparable standardized noise annoyance scales using the same method. In Korea the survey was conducted in four areas such as Seoul, Taejon, Taegu and Kwangju. About 100 subjects participated in each area approximately. The 21 adverbs were first in the early survey, and five verbal annoyance modifiers were finally constructed as follows;. 1 (Jeonhyo), 2 (Jokm), 3 (Bikyojerk), 4 (Ajoo), 5 (Umcheongnage)

The headphone is regarded as the most effective means for reproducing 3-dimentional virtual sound due to its channel separation property. However, there still exist several serious problems in headphone reproduction, such as, 'front-back confusion' and in-head localization'. These well-known problems are in general assessed by the subjective test that is based on human judgment. In this paper, an objective test is conducted in parallel with the subject test in order to validate the objective reproduction performance. Such a combined approach may be a more scientific and systematic approach to the reproduction performance.

Existing loudness models are specified only to diotic sounds in spite of the fact that normal human beings hear dichotic sounds. Approximately, the arithmetic mean of loudness values of both ear signals has been suggested for the resultant perceived loudness. In this study, the dependence of overall loudness perception on the interaural level differences was investigated by the subjective tests. It was found that the larger the interaural level difference, the louder the perception than the mean of calculated loudness values at both ears and the lower the critical band rate or the reference level, the louder the perception than the mean value. A modified loudness model was proposed to he applicable to dichotic sounds by using the equivalent diotic levels.

Until now, product mostly has revealed physical quantities created by the standpoint of engineers. Consumers, however, perceive and evaluate products on the non-physical characteristics, such as feelings, emotions, and experiences in different social and cultural situations. Especially, for the household appliances fur instance air-conditioner or refrigerator, the sound is heavily related to the satisfaction of a customer who is a real user of the product and is very important factor to decide purchasing as well as visual design. Therefore, in this research, the general tendency of consumer's psychology was investigated for the appliances. And also, in order to obtain clear guidelines for sound manipulation, the characteristics of the sound of air-conditioning systems and refrigerators were compared with others. Since it is important to overcome the discrepancy between engineering and marketing, the relevance of sound manipulation must be documented from the consumer's perspective. That is the reason why we conducted a consumer and marketing oriented study.

Rumbling sound is one of the most important interior sound of a passenger cu. The conventional rumbling noise research was focused on the reduction of the A-weighted sound pressure level. However A-weighted sound pressure level can not give the whole story about the rumbling sound of a passenger car. In this paper, we employed sound metric which is the subjective parameter used in psycoacoustics. According to recent research results, the relation between sound metrics and subjective evaluation is very complex and has nonlinear characteristics. In order to estimate this nonlinear relationship, artificial neural network th[ ory has been applied to derivation of sound quality index fur rumbling sound of a passenger car.

When we carry out acoustic holography, step-by-step measurement provides us larger aperture size with same number of microphones. But when we carry out step-by-step measurement, it is blown that sound signal must be stationary. However, when transfer function between input and output signal is time-invariant, we can apply step-by-step measurement to acoustic holography even if sound signal is transient We have to do only some Processing on signals from step-by-step measurements to make the signal data of each step compatiable with other steps. This paper accounts for that processing method.

There are many difficulties to get the scattered field generated by obstacle which has arbitrary shape or irregular surface impedance by using analytic solution or numerical methods. In this study, we propose experimental method of acoustic scattering holography that can predict the far-field scattered field based on nearfield measurements. In particular we can get the scattered fields of each wave-number components of incident fields. We express the relationship of wave-number components between incident fields and scattered fields using scattering matrix which is transfer matrix of wave-number components. Lastly, we prove the relation between wave-number components of incident and scattered field by experiments. The errors which are caused by measurements and decomposition methods are also analyzed.

The system in which a microphone and a loudspeaker are simultaneously used can cause an echo. The echo is caused by feedback between the output of the loudspeaker and the input of the microphone. The acoustic echo canceller is a device to cancel the echo in a communication system. Its general procedure for cancellation is first estimating the plant response of the feedback path and then eliminating the feedback signal from the input signal. In this paper, full-band and sub-band approaches are compared by using some simulation examples.

This paper proposes a method to generate virtual intensity field in space. The sound field of a zone enclosing the listener position is controlled to have maximum acoustic intensity to the desired direction. In order to control acoustic intensity of a zone, space-averaged active intensity is introduced. The ratio of space-averaged active intensity and control effort is defined as a cost function and expressed as a function of source control signals. It is shown that the cost function represents radiation efficiency of multiple sources. The control signals maximizing the cost function is found through eigenvalue analysis. The proposed method is verified by numerical simulations performed in free field condition, and the results provide a relation between wavelength and the size of controllable intensity field.

The transmission loss coefficient is very important acoustic property in parallel with absorption and acoustic impedance categorizing the acoustical materials, which can control the acoustical problems. At the same time, the transmission loss coefficient is a key parameter to choose the optimum material for the analysis of acoustical characteristics of material using SEA(Statistical Energy Analysis). In this paper, the transmission loss coefficient measurement system using 4-microphone impedance tube is proposed, based on the idea calculating the full transfer matrix of the acoustical sample to test. The theoretical background and measurement system are introduced, and finally the measurement results are verified.

The paper deals with the relationship between the eigenvalue branches and the corresponding flutter modes of cantilevered pipes with a tip mass conveying fluid. Governing equations of motion are derived by extended Hamilton's principle, and the numerical scheme using finite element method is applied to obtain the discretized equations. The order of branches and unstable modes associated with flutter are defined in the stability maps of mass ratios of the pipe and the critical flow velocity. As a result, the relationship between the flutter related to the eigenvalue branches and the flutter modes are investigated thoroughly.

To investigate the group plugging effect the fluid-elastic instability analysis has been performed on various column and row number of the KSNP steam generator lutes. This study compares the stability ratio of the plugged tube with that of the intact one. The information on the thermal-hydraulic data of the steam generator have been obtained by using the ATHOS3-MOD1 code with and without the thermal energy transfer at the plugged region. Both of the boundary conditions of hot-leg temperature and feedwater mass flow rate are fixed for this investigation. From the results of this study the stability ratios inside the group plugging zone are decreased slightly. At the outside of group plugging zone, however, most of the stability ratios tend to be increased.

The non-linear dynamic characteristics of a semi-circular pipe conveying fluid are investigated when the pipe is clamped at both ends. To consider the geometric non-linearity for the radial and circumferential displacements, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe, considering the fluid inertia forces as a kind of non-conservative forces. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the dynamic characteristics of the system, the discretized equations of motion are derived form the Galerkin method. The natural frequencies varying with the flow velocity are computed fen the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. Finally, the time responses at various flow velocities are directly computed by using the generalized- method. From these results, we should to describe the non-linear behavior to analyze dynamics of a semi-circular pipe conveying fluid more precisely.

Vibration characteristics of a fuel rod to be used in KALIMER(Korean Advanced LIquid MEtal Reactor) have been estimated through 3-dimensional finite element analysis and verified by experiment. The fundamental natural frequencies are found to be 6㎐ in air and 2.5㎐ in water. respectively. It has been found that in-water natural frequencies of the fuel rod are lower than in-air ones due to the added mass effect of the fluid filled inside the outer cylinder and they further decreases as the gap between the fuel rod and the outer cylinder increases, namely the added mass effect increases as the gap increases(maximum 54%). It has been also shown that the mass of the wire wrap axially coiled around the fuel rod do not affect the natural frequencies.

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported pipe conveying fluid subject to the moving mass. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass and the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The presence of crack results in higher deflections of pipe. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow and the crack severity are increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The time which produce the maximum dynamic deflection of the simply supported pipe is delayed according to the increment of the crack severity.

This paper dealt with friction-induced vibrations in engineering practice, specifically arising at the moment of counterturn of two friction surfaces. The harshness of the vibrations are attributed to the sharp change of the friction coefficients from kinetic to static near zero relative velocity, which is one of the examples of the stick slip. But the experimental results and numerical analysis of piston and cylinder operation showed that transition of the friction coefficient from kinetic to static is insignificant in vibrations. Dry friction itself dominates the harshness of vibrations. This study shows that how dry friction triggers the vibrations and demonstrates the effect of sharp transition from kinetic to static friction coefficient on the vibrations.

This paper presents an acoustic source localization technique on 2D cavity model in flow using a phased microphone way. Investigation was performed on cavity flows of open and closed types. The source distributions on 2D cavity flow were investigated in anechoic open-jet wind tunnel. The array of microphones was placed outside the flow to measure the far field acoustic signals. The optimum sensor placement was decided by varying the relative location of the microphones to improve the spatial resolution. Pressure transducers were flush-mounted on the cavity surface to measure the near-filed pressures. It is shown that the propagated far field acoustic pressures are closely correlated to the near-field pressures. It is also shown that their spectral contents are affected by the cavity parameter L/D.

Recently, high noise problem was experienced during the development of 2-pole squirrel cage motor for industrial compressor. In order to firstly identify the noise characteristics, a variety of measurements were carried out. It was found out that high noise was dominated by linear and nonlinear slot noise components. For the development of low noise indusrial motor, the air gap between rotor and stator in the motor was firstly enlarged. Secondly, it was also modified for the cooling housing to have high absorption features. Consequencely, low noise 2-pole motor having the noise level of less 80㏈(A) was developed. In this paper, a series of noise identification and control process for this motor are introduced.

The common practice to reduce the compressor noise is installing a muffler. The noise reduction performance of the muffler is the most critical one for the total noise characteristics of the compressor. In this paper, a simple impedance approach using the concept of transmissibility is employed for the acoustic analysis of the muffler, It is known that transmissibility is directly related to insertion loss, and thus transmissibility can Indicate the correct performance of the muffler. The analysis result is supported by a Finite Element Model. In addition, some experiments conducted also show that the transmissibility is mildly related to the measured sound pressure outside the compressor.

The present experimental study deals with noise reduction and improvements in cooling performance in a plasma display panel(PDP) television (TV). To reduce the noise, the effects of installation parameters are studied. The experimental parameters under investigation are the distance between the fan and the rear case of a PDP TV, position of the strut on the fan, and the fan RPM. The variance of RPM is the most significant facto., and a 250 RPM decrease from 910 RPM causes about 4㏈(A) reduction in the system noise. To increase performance, flow characteristics are investigated by using a visualization technique and measuring the volume flow rate. The visualized results show that a radial direction flow due to large system resistance is significant, and an axial velocity oscillation is observed from the measurement of the volume flow rate. To prevent both a radial direction flow and an axial velocity oscillation, sponges are inserted in the space between f3n and the rear case. Inserted sponges improve the volume flow rate of cooling fans up to 32% since they convert a radial direction flow to an axial direction flow. Also an axial velocity oscillation with large amplitude and low RPM disappears. Increasing volume flow rate causes the PDP TV to improve its cooling performance. Additionally the same volume flow rate can be obtained with a decreased fan speed due to the inserted sponge. Noise reductions of 4.2 ㏈(A) at the rear and 1.1 ㏈(A) at the front of the TV are obtained by the decreased RPM. An increase of 10% of the volume flow rate is also achieved by inserting sponges.

Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-.oiling system (MD-ARS) might be one candidate of several systems against the ship's rolling. As the movable range of the mass on the ship is finite, the control system must include restriction on the mass position to protect the device and the ship. This restriction usually causes windup phenomenon and control performance is deteriorated seriously. We adopt anti-windup technique to improve the control performance and demonstrate its efficiency by simulation.

Recently, the buckling is easy to happen a thin plate and High Tensile Steel is used at the structure so that it is wide. Especially, the buckling is becoming important design criteria in the ship structure to use especially the High Tensile Steel. Consequently, it is important that we grasp the conduct after the buckling behaviour accurately at the stability of the body of ship structure. In this study, examined closely about conduct and secondary buckling after initial buckling of thin plate structure which receive compressive load according to various kinds aspect ratio under simply supported condition that make by buckling formula in each payment in advance rule to place which is representative construction of hull. Analysis method is F.E.M by ANSYS and complicated nonlinear behaviour to analyze such as secondary buckling.

In general, the essential requirement for cruisers or car ferries is the reduction in noise to ensure high quality and comfort. Recently, the Ro-Ro Passengers Ferry (ROPAX) was built in Hyundai Heavy Industries. In order to minimize the noise levels, careful attention have to De paid by the special committee of experts from the initial design stage to the sea trial. Proper countermeasures, considering the characteristics of sources and receiver spaces, were applied from the noise prediction and various experiment results. Finally, this ship was successfully delivered with excellent noise properties. This paper describes the procedure of noise analysis, the countermeasures of noise control, and the measurement results of the sea trial. Onboard noise analysis had been carried out by statistical energy analysis program and outdoor noise prediction program based on ISO9614. The prediction results are in good agreements with the measurement results. The technology to minimize the noise levels for cruisers or car ferries has been established throughout the construction of this ship.

As for marine propulsion shafting system using 4 stroke diesel engine, it is common to apply reduction gear box between diesel engine and shafting with a view of increasing mechanical efficiency, which inevitably require elastic coupling due to avoid chattering and hammering inside of gear box. In this study, optimum method of rectifying propulsion shafting system in case of 750ton fishing vessel specially in a view of torsional vibration, is theoretically studied. After exchange of diesel engine and gear box, analysis result of torsional vibration get worse and so some countermeasure are needed. The elastic coupling is modified from present block type rubber coupling showing relatively high torsional stiffness to rubber coupling with two series elements directly connected. The vibration measurement using two laser torsion meters was done during sea trial, whose results are compared to those of calculation and verified.

In this paper, we introduce the measurement of the underwater noise with 32channel hydrophone array of Samsung CAvitation Tunnel (SCAT) and the detection technique of noise sources by using the beam-forming method. Measurement and way signal Processing under fluid flow are essential works for the underwater acoustics, especially for the detection of noise sources. As the acoustic impedance of the water is relatively high and the tunnel is an enclosed system, we have to consider the interaction between tunnel and water together with the reflection of noise in the beam-forming technique. Also, for a hydrophone array system that is fixed on one side of tunnel wall as done in SCAT is liable to suffer from some limitations in the detection of the noise sources with the array, we discuss these limitations particularly on the frequency range and spacing of noise sources.

Recently, the development of mobile devices demands information storage systems to use micro drive devices and cheap media. These should have several characteristics, for example, the subminiature of size, the robustness of shock, the minimum of cost and power consumption, and the removability of multiple applications. A conventional optical disk drive is more suitable for these specifications than the others. The optical storage system of the new generation to use a blue laser and a high numerical aperture (NA) is the perfect candidate for micro optical disk drives. In this paper, the micro actuator that can be applied to a micro optical disk drive is designed by response surface methodology to use a structural analysis and an electro-magnetic analysis. Based on above results, the coarse actuator and fine actuator are designed and improved from the point of view of the size and the power. Consequently, the designs of a micro actuator are proposed through these courses.

본 연구에서는 적층형 압전소자를 이용하여 초소형 및 슬림형 광디스크 드라이브용 광픽업 구동기를 개발하였다. 최근에 휴대용 정보기기의 급격한 발달로 인해 다양한 형태의 초소형 정보저장기기가 사용되고 있으며 착탈식 형태의 초소형 광디스크를 사용하는 ODD가 개발 중에 있다. 적층 형태의 압전소자와 유연 힌지 형태의 변위 확대기구를 사용하여 구동기의 출력 힘과 허용 변위를 증가시키도록 설계하였다. 압전형 구동기의 동특성을 고려한 모델링과 이론적 해석을 통해 목표 변위와 성능을 만족하도록 설계 변수를 최적화하였고 이를 ANSYS를 이용한 해석과 비교하였다. 상용화된 적층형 압전소자를 이용한 prototype 올 제작하여 실험을 수행하였으며 이론적인 예상 값과 잘 일치함을 보였다. 이와 같은 이론적 해석과 실험 결과를 토대로 높이가 2.5mm이며 15V 에서 $\pm$400$\mu\textrm{m}$의 변위를 갖는 슬림형 및 초소형 ODD에 적합한 압전형 구동기를 설계하였다.

We propose the re-design method of modal parameters to depress the 2nd resonance peak of the ultra-slim-height optical pick-up actuator. With the addition of tile counter mode near the 2nd resonance frequency, we can achieve the gain margin which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.

Recently, a new type actuator using multi-pole magnet has been developed for high-density and high-speed disk drive, which can be achieved higher sensitivity than a conventional actuator for applying one-pole magnet. However, it is very difficult for the actuator of multi-pole magnet to meet simultaneously the optimal design condition for reducing rolling mode effect and improving driving sensitivity because the force center is different from the mass center In this paper, First We propose the new shape coil for tracking which can reverse moment additionally in tracking motion, Next we achieve the optimal design to reduce phase disturbance and peak gain at the rolling mode frequency. Finally, the validity of the proposed methods is proved from experimental results.

Recently the trends in information storage devices need small size, mobility, high capacity, and low power consumption etc. To satisfy those, the development of high performance actuator is an important issue. Compared with general linear actuator for optical disk drive, swingarm type rotary actuator is suitable to design in small form factor and has fast access time for random access. Swingarm actuator is designed considering the structural problem and the actuating force of VCM(Voice Coil Motor). The increase of mass caused by optical components makes vibration problems of swing-arm, therefore resonance frequency should be increased and inertia has to be reduced. ANSYS FEM tool is employed in optimizing swingarm. The VCM is designed using 3-D electro-magnetic analysis, and parameters of magnetic circuit are determined to matte large flux density. The large flux density enables to achieve low power consumption. VCM holder is designed to get the mass balance of total actuator and this balance reduces the magnitude of critical mode relative to pivot bearing, It is expected that swingarm type rotary actuator designed by this method is available to variable type of micro optical disk drives.

The purpose of this research is to observe that the acoustic characters of classroom have some difference by several conditions. TSP has used to measure impulse response and such physical indexes as RT(Reverberation Time), D$\sub$50/, and STI(Speech-Transmission-Index) are computed by it. we investigate difference under some conditions such as when students were present at each classroom and when was not so, and when professor used a microphone and unused it. In this study, we found that reverberation time when people take a seat is lower than was not so. we wish to help one who work for construction industry, as they build a kind of classroom

Some basic guidelines for changing non-uniform boundary condition in an acoustically small cavity are presented. In this paper, modal summation technique is used to represent inside sound field. From this formulation, corner effect is defined and proposed. The corner in a cavity is good position for changing boundary condition effectively. Impedance circle with same absorption coefficient is defined to find appropriate impedance of absorptive material for better noise control performance.

The Statistical Energy Analysis is based on the power flow and the energy conservation between sub-systems, which enable the prediction of acoustic and structural vibration behavior in mid-high frequency ranges. This paper discusses the identification of SEA coupling loss factor parameters from experimental measurements of small reverberation chamber sound pressure levels and structural accelerations. As structural subsystems, steel plates with and without damping treatment are considered. Calculated CLFs were verified by both transmission loss values for air-borne CLF case and running SEA commercial software As a result, CLFs have shown a good agreement with those computed by software. Acoustical behavior of air-borne noise and structure-borne noise has been examined. which shows reasonable results, too.

International Convention Center Jeju(ICCJ) was planed and built for accommodating a variety of conventional and exhibitional activities. For a better flexibility of operation, almost all rooms in ICCJ are designed to be subdivided Into a couple of small rooms with installation of movable partition walls. Architectural and acoustical design should be deliberatively and cooperatively undertaken to cope with such a complex condition. Conference hall, the largest room in ICCJ, has a capacity of 5000 seats who:1 used as a whole. It could be divided into 3 halls, one with 2000 pre-installed seats on slanted floor, up/down removable stage and its settings above, and the other 2 flat rooms with no seats installed. A devided hall with pre-installed seats and stage is designed for a multi-use auditorium. Almost all surfaces except ceilings adjacent to the stage are sound absorptively treated, in regard to extensive use of sound reinforcement systems. Its reverberation time 1.65 sec without audience, which is roughly correspond to 1.50 sec with fully occupied audience. When there is a need for a larger room, all the partition wail Is removed and the hall could be used as a whole. Exhibition hall is located in the first floor of ICCJ. Absorption and softness are needed for the hat 1 because exhibition behavior has something noisy features. Perforated MDF panels with porous materials and air space in the back groundare adopted for the walls. There are one large, two medium, and several small convention rooms in ICJJ. The room are also acoustically designed for maximum flexibility with no defects soundwisely.

최근에 이르기까지 문화예술회관들이 대중들의 문화적인 욕구에 의하여 많이 건립되었으나 대중들과 음악가와 연주자들을 도외시한 채 건축음향 기획 없이 건립되어진 많은 문화예술회관들이 지방자치시대를 맞이하여 지방재정에 적잖은 부담으로 작용하고 있으며 또한 민영화로 독자적으로 운영을 하지 않으면 안되게 되었다. 이와 같은 경쟁체제에서 많은 문화예술회관들이 음향문제로 많은 어려움을 겪고 있으나 대책은 미미한 실정이다. 본 연구는 U문화예술회관의 대공연장을 중심으로 대공연장의 음향특성을 측정분석하고 최근 6년간의 공연장의 장르별 이용률을 기초 자료로 활용하여 측정 결과를 중심으로 대공연장의 개선방향을 설정하고 음향 시뮬레이션를 통한 음향인자를 (잔향시간 (RT60, EDT), 명료도(C80, D50), LF, 음압레벨) 비교분석 평가하였다. 그리고 설계에 반영 벽체에 음향 보강 반사판을 시설하고 분석하여 리모델링 공사 후 음향특성이 개선됨을 확인할 수 있었으며 벽체에 시공된 반사판의 효능을 입증할 수 있었다.

The objective of this paper is to develop an experimental technique to measure the in-plane vibration intensity of a plate. In order to measure the in-plane vibration intensity at a data point, the frequency response functions for the 2 components of an acceleration vector are measured at each point of 4 points in the neighborhood of the data point. This experimental technique has been implemented to measure the in-plane vibration intensity of a plate. The experimental result has been compared with a theoretical result. It showed that the experimental technique can be effectively used to measure the in-plane vibration intensity of plates.

Leaks in underground pipelines can cause social, environmental and economical problems. One of a good contermeasures of leaks Is to find and repair of leak points of pipes. Leak noise is a good source to identify the location of leak points of pipelines. Although there have been several methods to detect the leak location with leak noise, such as listening rods, hydrophones or ground microphones, they were not so efficient tools beca. In this paper, two accelermeters are used to detect leak locations which could provide an easier and efficient method. The filtering, signal processing and algorithm is described for the detection of leak location. A 120m-long pipeline system for experiment is installed and the results with the system show that the algorithm with the two accelerometers gives very accurate pinpointing of leaks. Theoretical analysis of sound wave propagation speed in underground pipes is also described.

There has been a number methods for the presentation of time-frequency analysis of non-stationary signal. In this paper, STFT(short time Fourier transform), wavelet transform, Wigner distribution, and higher order Wigner distribution are discussed in details with simulation signals. They are also applied to the analysis of the wave propagation of a semi finite beam. Wigner distribution and higher order Wigner distribution have good time-frewuency resolutions. Wavelet transform is required for impact analysis but should be applied carefully. STFT suffers from time-frequency resolutions. Each method is has its advantage and disadvantage depending on each application signals.

The problem of elastic wave resonance scattering from elastic targets is studied in this paper. A new resonance formalism to extract the elastic resonance information of the target from scattered elastic waves is introduced. The proposed resonance formalism is an extension of the works developed for acoustic wave scattering problems by the author. The classical resonance scattering theory computes reasonable magnitude information of the resonances in each partial wave, but the phase behaves in somewhat irregular way, therefore, is not clearly explainable. The proposed method is developed to obtain physically meaningful magnitude and phase of the resonances. As an example problem, elastic wave scattering from an infinitely-long elastic cylinder was analyzed by the proposed method and compared to the results by RST. In case of no mode conversion, both methods generate identical magnitude. However, the new method computes exact $\pi$ radian phase shills through resonances and anti-resonances while RST produces physically unexplainable phases. In case of mode conversion, in addition to the phase even magnitudes are different. The phase shifts through resonances and antiresonances obtained by the proposed method are not exactly $\pi$ radians due to energy leak by mode conversion. But, the phases by the proposed method show reasonable and intuitively correct behavior compared to those by RST.

This paper introduces multichannel blind source separation (BSS) and multichannel blind deconvolution (MBD) based on higher order statistics of signals from convolutive mixtures. In particular, we are concerned with the case that the number of inputs is the same as the number of outputs. Simulations for two input two output cases are carried out and their performances are assessed. One of the major applications of those sequential algorithms (BSS and MBD) is demonstrated through the fault signal detection from only a single measurement of rotating machine, which offers a certain degree of practicability in the engineering field such as machine health monitoring or condition monitoring.

The differential equations governing free, in-plane vibrations of non-circular arches with non-uniform cross-section, including the effects of rotatory inertia, shear deformation and axial deformation, are derived and solved numerically to obtain frequencies. The lowest four natural frequencies are calculated for the prime parabolic arches with hinged-hinged, hinged-clamped, and clamped-clamped end constraints. Three general taper types for rectangular section are considered. A wide range of arch rise to span length ratios, slenderness ratios, and section ratios are considered. The agreement with results determined by means of a finite element method is good from an engineering viewpoint.

This paper has the object of investigating natural frequencies of thick plates on inhomogeneous Pasternak foundation by means of finite element method and providing kinematic design data lot mat of building structures. This analysis was applied for design of substructure on elastic foundation. Mat of building structure may be consisdered as a thick plate on elastic foundation. Recently, as size of building structure becomes larger, mat area of building structure also tend to become target and building structure is supported on inhomogeneous foundation. In this paper, vibration analysis or rectangular thick plate is done by use or serendipity finite element with 8 nodes by considering shearing strain of plate. The solutions of this paper are compared with existing solutions and finite element solutions with 4${\times}$4 meshes of this analysis are shown the error of maximum 0.083% about the existing solutions. It is shown that natrural frequencies depend on not only Winkler foundation parameter but also shear foundation parameter.

In the practical engineering fields, the horizontally curved beams are frequently erected as the major/minor structural components. The effects of both variable curvature and variable cross-section on structural behavior are very important and therefore these effects should be included in structural analyses. From this viewpoint, this paper deals with the free vibrations of horizontally curved beams with variable curvature and variable cross-section. In this study, the parabola as the curvilinear shape and stepped beam as the variable cross-section are considered. The ordinary differential equation governing free vibrations of such beams are derived. For calculating the natural frequencies, the governing equations are solved by numerical methods. The Runge-Kutta and Determinant search Methods are used for integrating the differential equations and for calculating the natural frequencies, respectively. With regard to numerical results, the relationships between frequency parameters and various beam parameters are presented in the forms of Table and Figures.

The purpose of this paper is to investigate the free vibration characteristics of tapered beams with translational and rotational springs and point masses at the ends. The beam model is based on the classical Bernoulli-Euler beam theory which neglects the effects of rotatory inertia and shear deformation. The governing differential equation for the free vibrations of linearly tapered beams is solved numerically using the corresponding boundary conditions. Numerical results are compared with existing solutions by other methods for cases in which they are available. The lowest four natural frequencies are calculated over a range of non-dimensional system parameters.

This paper deals with the free vibrations of horizontally curved beams with the general boundary condition, which consists of translational and rotational springs. The equations of general boundary condition of such beams are derived, while the ordinary differential equations governing free vibrations are adopted from the literature. The parabola as the curved beam's curvilinear shape is considered in numerical examples. For calculating the natural frequencies, the governing equations are solved by numerical methods. The Runge-Kutta and Determinant Search Methods are used for integrating the differential equations and for calculating the natural frequencies, respectively. for validation purpose, the numerical results obtained herein are compared to those obtained from the SAP 2000. With regard to numerical results, the relationships between frequency parameters and various beam parameters are presented in the forms of Table and figures.

This study focused on to design and toanalysis of a myoelectronic hand. We considered a low frequency factor in human life and to quantify low frequency which a human body responded to using a 1-axis ant a 3-axis accelerometer. The dynamic myoelectronic hand are important for tasks such a continuous prosthetic control and a EMG signal recognition, which have not been successfully mastered by the most neural approached To control myoelectronic hand, classifying myoelectronic patterns are also important. Experimental results of FEM are 110㎫ on Thumb, 200㎫ on Index finger, 220㎫ on Middle finger 260㎫ on Ring finger and 270㎫ on Little finger. Experimental results of accelerometer are 1.4-0.4(m/s2) ,(5-20(〔Hz〕) in Feeding activity and 0.4-0(m/s2) (0-10〔Hz〕) in Lifting activity. Considering these facts, we suggest a new type myoelectronic hand.

This paper presented a design and control of a new RGO(reciprocating gait orthosis)and its simulation. The new RGO was distinguished from the other one by which had a very light-weight and a new RGO(reciprocating gait orthosis) system. The vibration evaluation of the hip joint system on the new RGO(reciprocating gait orthosis)was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 ㎐. The gait of the new RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the new RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties, we made the hip joint system of FEM and the hip joint system by 1-axis and 3-axis Accelerometers.

This study was tested for the bending stress analysis of Experimental stress analysis on various ankle foot orthoses(AFOs) was fulfilled. Stress was measured by Strain gages which were attached on 8 region in AFOs Results revealed that the peak compressive/tensile stress in the orthoses occured in the lateral region of neck. The Stress Analysis system was made by the electronic oscilloscope, strain gage sensors, amplifier, A/D converter, PC with C program It will be able to using the important data in splint design. Selected AFOs were some different materials but all have same shape except one type(orthosis with joint). C program Is used for managing data. Thus lateral side of the neck region is failed easily.

A new type of the Expanded Knee brace was developed to measure the human knee joint. This instrument was composed of six parts, four arranged for two hinge joints and two pin joint , and two hinge for the expanded system. With a developed instrument, the experimental results obtained the data of Accelerometer, the experimental results obtained of the data FEM, the experimental results obtained the data of Motion Analysis and Force platform. Compared to earlier developed sports type knee brace, new instrument shows its convenience in application and accuracy in measurement.

This study was tested for the bending stress analysis of hand spl int for Hemiplegic Patients. Hemiplegia was represented the stroke and the cerebral palsy. Hand splints of four materials was an Orthoplast hand splint, a Polypropylene hand splint, a Yogips hand splint and an Aluminum hand splint. The Stress Analysis system was made by the electronic oscilloscope, strain gage sensors, amplifier, A/D converter, PC with C program. It will be able to using the important data in spl int design. The results of analysis were obtained various different graphes and maximum data in an Orthoplast hand splint, a Polypropylene hand splint, a Yogips hand splint and an Aluminum hand spl int.

One of the methods that are used to compare and verify the supporting performance of the spacer grids developed is the vibration characteristic test. A modal test in this paper is performed for a dummy rod 3,847mm tall supported by eight New Doublet (ND) spacer grids. For the vibration test in air, nine accelerometers, one displacement sensor and one shaker are used for acquiring signals, and an I-DEAS TDAS software is employed for analyzing the signals. Also, a finite element (FE) analysis is performed by a beam-spring simple model and a contact model simulating the contact phenomenon between the rod and the fm spring. And then, the result of the FE analysis is compared with that of the modal test. The natural frequencies as well as the mode shapes calculated by the proposed contact models have a greater similarity to the test results than those by the previous beam-spring model. In addition, for grasping whether or not the modal parameters are influenced by where shaking spot is, two kinds of tests are performed; one is for the shaker attached at the fourth span (center), the other is for the shaker at the fifth span that is one span nearer to the bottom of the rod. The latter shows higher MAC than the former. Finally, the vibration displacements are measured in the range of 0.112-0.214mm for the excitation force of 0.25-0.75 N.

A method for the dynamic analysis of thin-walled cylindrical shell conveying steady fluid flow presents. The dynamics of thin-walled shell is based on Sanders' theory and the fluid flow in cylindrical shell is treated inviscid, incompressible fluid. A dynamic coupling conditions at fluid-structure interface is used. The equations of motion are solved by a finite element method and validated by comparing the natural frequency with other published results and Nastran. The influence of fluid velocity on the frequency response function is illustrated and discussed.

The sloshing phenomenon sometimes happens to occur in a liquid fuel tank due to the unexpected and/or inevitable vibrating conditions and may result in severe effects on the structural stability. This study deals with the development of experimental techniques for the evaluation of sloshing behaviors in the liquid fuel tank and for the identification of natural frequencies and mode shapes by varying with various vibrating conditions. Measurements of the pressure and load acting on the side surface of vibrated liquid fuel tank are carried in order to identify the effects of sloshing phenomenon by using various types of baffles. The results show that the baffles can be used to minimize the sloshing phenomenon in liquid fuel tank effectively

An analytical method for the free vibration of single circular plate submerged in a fluid-filled rigid cylindrical vessel was developed by the Rayleigh-Ritz method based on the Fourier-Bessel series expansion. It was assumed that the plate is clamped at an offcentered location of the cylinder, and the non-viscous incompressible fluid contained in the cylinder is bisected by the plate. It was found that the theoretical results can predict well the fluid-coupled natural frequencies with excellent accuracy comparing with the finite element analysis results. The offcentered distance effect on the natural frequencies was also observed.

본 연구는 비압축성 유동에 노출되어 있는 2-D wing-flap 시스템의 공탄성 응답의 능동제어를 다루고 있다. 본 연구 논문의 목표는 LQG 제어법칙을 수행함으로써 임계 비행속도하에서 플러터의 비안정성을 억제하고 돌풍이나 blast load에 의한 임계 공탄성 응답의 성능을 향상시키는 것과 동적응답을 감쇠하는 수행능력들을 증명하는데 있다.

When oil pressure of damper is lost or relative stiffness of spring drops in vibration system, it can be fatally dangerous situation. A fault diagnosis method for vibration system using Support Vector Machine(SVM)is suggested in the paper. SVM is used to classify input data or applied to function regression. System status can be classified by judging input data based on optimal separable hyperplane obtained using SVM which learns normal and abnormal status. It is learned from the relationship of system state variables in term of spring, mass and damper. Normal and abnormal status are learned using phase plane as in put space, then the learned SVM is used to construct algorithm to predict the system status quantitatively

In accordance with the tendance to construct high-rise apartment buildings, the elevators tend to high speed up and to the drive more frequently. So, the problem of vibration and noise produced by the operating elevator has been treated as an important subject all the more. In this research, the actual levels of vibration and noise which generated and transmitted by the elevator operation in apartment buildings were measured and these characteristics were analysed to examine the countermeasures to be able to reduce the these vibration and noise level, and to design the several vibration and noise control.

A High-speed cutter, a kind of electric tool is studied to reduce its vibration and noise. The experimental modal analysis, the operational deflection shapes(ODS) and the time domain analysis(TDA) are used in the SMS software to analyze the vibration signals from an operating high-speed cutters under steady state operating condition. The second mode and fifth m,)do of the base plate coincide with the driving frequencies of the motor, And the vibration of the wheel cover is caused by the gap between the main wheel cover and the sub wheel cover. The structural modification for the base plate was done to reduce the vibration. The effect of modification is verified through the test.

This paper introduces an enhanced condition monitoring and diagnosis system recently developed for rotating machinery. In the system, the data aquisition/monitoring signal processing, machine condition classifier, case-based reasoning and demonstration modules are effectively integrated with user-friendliness so that machine operators can easily monitor and diagnose the status of rotating machinery in operation. Some of the new features include the directional spectrum, case-based reasoning and neural network techniques. And the demonstrator modules for fault diagnosis of a Bear driving system and for basic understanding of the rotor dynamics are provided to help the potential users better understand the system.

In the semiconductor and the optical industry a new transport system which can replace the common system is required. The common systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system solve these problem. In this paper the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave get orators are performed. The effect of transporting speed according to the change of weight and amplification voltage are verified. In addition, the system performance for actual use is evaluated.

Sound intensity method is well known as a visualization technique of sound field and sound propagation in noise control. Sound intensity is a vector quantity that describes the magnitude and the direction of net flow of acoustic energy at a given position. The current measuring method is expensive and difficult to identify the noise source exactly. In this paper, we have studied the noise source identification and the characteristics of noise source of rotary compressor for air conditioner using complex sound intensity method. The new method for instantaneous sound intensity is also proposed and it is useful for transient state and steady state. The criteria of these state, select auto correlation coefficient. The advantage, simplicity and economic attribution of this method are verified by analyzing the characteristics of noise source with instantaneous sound intensity compared to mean sound intensity.

Hermetic rotary compressor is one of the most Important components for air conditioning system since it has a great effect on both the performance and the noise and vibration of He system. Noise and vibration of rotary compressor is occurred due to gas pulsation during compression process and unbalanced dynamic force. In order to reduce noise and vibration. it is necessary to identify sources of noise and vibration and effectively control then. Many approaches have been tried to identify noise sources of compressor. However, compressor noise source identification has proven to be difficult since the characteristics of compressor noise are complicated due to the interaction of the compressor parts and gas pulsation. In this work, Statistical Energy Analysis has been used to trace the energy flow in the compressor and identify transmission paths from the noise source to the sound field.

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way(nl- directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding Point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure

Vibration and Noise of air conditioner are entirely determined by compressor vibration. Compressor vibration transmitted to the enclosure of air conditioner or Pipes connected compressor with heat exchanger. Enclosure generated noise and vibration. Therefore, the analysis of compressor vibration analysis is considered significant technical issue. For the reduction of vibration of compressor, it is necessary to grasp correctly vibration transmission paths and excitation sources in the compressor shell. Because, shell (Surface of compressor) shows whole vibration characteristic of compressor mechanism. In this paper, vibration intensity was applied to measure vibration energy flow on the shell. From this technique, it is possible to catch the path of vibration propagation along the one cycle and the location of vibration energy sources may change with time on the shell.

A Dynamic vibration absorber(DVA) is developed to reduce the excessive vibration of an optical disk drive(ODD) originated from the deriving range of an wobble disk and unbalanced disk. We design the material properties and shapes of the DVA by simulating Frequency response function(FRF) such as target frequency, mass of the DVA, stiffness of damper, damping coefficient, shape and dimension, analyze dynamic characteristics and provide its design guide line for suppressing the vibration of an optical disk derive. To examine the performance of the DVA, the vibration of the feeding system with DVA and without DAA are measured by using a three-axis accelerometer, PCB derive and Pulse analyzer. The result show that the proposed DVA reduces the vibration of wide range in ODD.

With the rotational speed of the hard disk drive (HDD) increased, the low frequency structural vibration induced by the unbalance force gives rise to the structure home noise of the personal computer, and finally degrades the noise quality. As the unbalance of the hard disk drive is decided by the mechanical assembly allowance between clamping and platter disk, there is limit to control this unbalance by the improved assembly method. To improve the noise and vibration performance of PC, basically the unbalance of HDD needs to be measured absolutely and reduced during the stage of the disk assembly. This study introduces the HDD unbalance measurement methods of the absolute magnitude based on the mobility concept, and the unbalance location information with the acceleration orbit.

A flow field around a disc in an optical disc drive is invested using numerical methods. The high-speed rotating disc induces a strong flow field around the disc, which causes the pressure distribution on the surfaces of the disc. The pressure difference between the upper and the lower surfaces causes the deformation of the disc. In the first part of this study, flow fields around a rotating disc and a stationary wall are investigated using a similarity solution method, in order to identify the effect of the distance between the disc and the wall on the pressure distribution on the surfaces of the disc. In the second part, flow field in a slim-type optical disc drive is studied using a commercial code in order to consider the effect of the vortices generated by the local geometry of the drive.

The aerodynamically excited vibration and natural frequency of rotating CD and DVD disks are analytically and experimentally studied in this paper The theoretical analysis uses a fluid-structure model where the aerodynamic effects are represented in terms of elastic, lift and damping components. The explicit expression on natural frequency of the air coupled disk is obtained as functions of the three aerodynamic coefficients. The experiments performed using a vacuum chamber and CD/DVD disks rotating in vacuum, open air and enclosure give three main results. One is that the aerodynamic effect by the surrounding air reduces the natural frequencies and critical speeds of the vibration modes. The second is that natural frequency of disks rotating in open air is larger than that in enclosure. Finally, it is shown that the disk vibration is reduced as the gap between the disk and the rigid wall decreases.

Near-filed optical storage using cantilever aperture tip is a promising way fer next generation optical data storage. To enhance the speed of reading and writing data, gap between tip and media should be controlled fast and precisely within near field region. In this paper, several PZT actuators are analyzed far constructing dual servo control algorithm: coarse actuators(stact. PZT, bimorph PZI) for media surface inclination and One actuator(film PZT) for media surface roughness. Dynamic analysis of stack PZT, bimorph PZT, and film PZT are performed through the frequency response. Based on the frequency response and mathematical model, fast analog controller is designed.

VIPER a new tool for the VIsual PERception of sound quality and for sound design will be presented. Requirement for the visualization of sound quality is a signal analysis modeling the information processing of the ear. The first step of the signal processing implemented in VIPER, calculates an auditory spectrogram by a filter bank adapted to the time- and frequency resolution of the human ear. The second step removes redundant information by extracting time- and frequency contours from the auditory spectrogram in analogy to contours of the visual system. In a third step contours and/or auditory spectrogram can be resynthesised confirming that only aurally relevant information were extracted. The visualization of the contours in VIPER allows intuitively to grasp the important components of a signal. Contributions of parts of a signal to the overall quality can be easily auralized by editing and resynthesising the contours or the underlying auditory spectrogram. Resynthesis of time contours alone allows e.g. to auralize impulsive components separately from the tonal components. Further processing of the contours determines tonal parts in form of tracks. Audible differences between two versions of a sound can be visually inspected in VIPER through the help of auditory distance spectrograms. Applications are shown for the sound design of several interior noises of cars.

It is said that the goal of the design of good acoustical environment is at first the reduction of undesirable sounds, and in addition the introduction of desirable sounds by which our minds are soothed. The task of creating the desirable sounds leads to the realization of a comfortable acoustic environment and the design of soundscape. It may be an important starting point of soundscape design to select suitable sounds for the target spaces, because each space has a different surrounding condition and requires a special ambient sound. This paper aims to survey preference of the environmental sounds suitable for the public spaces in urban areas such as parks, bus terminals. 35 kinds of natural sounds are rated by 26 pairs of adjectives. The results of psycho-acoustic experiments are as follows. 1. The proper adjectives for expressing the environmental sounds are classified into 6 groups of comfort, pleasure, fullness, variety, distinctness, naturalness. 2. Bird singing, murmuring of a stream, artificial sounds, singing of insects and animals are the affirmative order of preference. 3. Green musics consisted of music and natural sounds are preferred to the pure natural sounds. 4. Sound level relative to background noise causes various preferences to natural sounds in public spaces.

It seems inevitable for residential buildings to be high-rise and allocated near traffic roads due to the overcrowding in urban area. Acoustic environment in those area has been seriously deteriorated by the increase of traffic vehicles. Commonly used sound barriers have a limitation in controlling noise due to diffraction noise of sound barrier. Hence sound barrier is not effective to attenuate noise especially for the residential units in high level. This work aims at evaluating noise reduction according to the tunnel section shape by using 1/5 scale model. We carried out a number of field measurements for 1/5 scale model of Noise Barrier Tunnel with various sectional shape. The results from predictions and the measurement show generally good agreement.

A successful design approach for noise barriers should be multidisciplinary because noise reduction goals influence both acoustical and non-acoustical considerations, such as maintenance, safety, physical construction, cost and visual impact These various barrier design options are closely related with barrier dimensions. In this study, we have proposed an optimal design method of noise barriers using simulated annealing algorithm, providing a barrier having the smallest dimension and achieving the specified noise reduction at a receiver region exposed to the industry and infrastructures, to help a successful barrier design.

Numbers of people living in high rise apartments are growing due to the overcrowding in urban area. Acoustic environment in those residential buildings has been seriously deteriorated by the increase of wheeled transports. Commonly used sound barriers have a limitation in controlling noise influencing higher part of a residential building. The use of noise barrier tunnels can be an alternative to supplement the defects of conventional noise barriers. But intensive measurements on noise levels at apartments vicinity of current noise barrier tunnels show that the tunnel now has a limited advantage on reducing the noise levels from arterial roads. The present work aims at providing an useful design tool In designing noise barrier tunnels for residential areas adjacent to roads. Number of field measurements, scale model measurements, and computer simulations were performed to ensure whether the prediction from scale model and computer simulation are appropriate. Result shows that the predictions from scale models and computer simulations could be valid prediction tools for designing sound barrier tunnels.

Although the holes on the shell case are very important fer the acoustic performance, it is difficult to solve the problem because the case includes thin bodies. Hence, in the past, only the method of trial and error, which depends on the engineer's intuition and experience, was available fur the design of holes. Many researchers have tried to solve the thin-body acoustic problems, since the conventional boundary element method (BEM ) using the Helmholtz integral equation fails to yield a reliable solution fer the numerical modelling of radiation anti scattering of sound from thin bodies. In the area of the analysis of thin-body acoustic problem, three approaches are generally used; the multi-domain BEM, the indirect variational BEM, and the normal derivative integral equation And there has been just a f9w study reported on the design optimization for the acoustic radiation problems by using only the conventional BEM. For the thin-body acoustics, however, no further study in the optimization fields has been reported. In this research, the normal derivative integral equation is adopted as an analysis formulation in the thin-body acoustics, and then used fur the optimization. The analytical approaches for the design of holes are proposed by using a topology optimization technique and a genetic algorithm. The proposed approaches are implemented and validated using numerical examples.

There are many industrial applications including thin-body structures such as fins. For the numerical modeling of radiation of sound from thin bodies, the conventional boundary element method (BEM) using the Helmholtz integral equation fails to yield a reliable solution. Therefore, many researchers have tried to solve the thin-body acoustic problems. In the area of the design sensitivity analysis (DSA) and optimization methods, however, there has been just a few study reported. Especially fur the thin-body acoustics, however, no further study in the DSA and optimization fields has been reported. In this research, the normal derivative integral equation is adopted as an analysis formulation in the thin-body acoustics, and then used for the sizing DSA and optimization. Since the gradient-based method is used for the optimization, it is important to have accurate gradients (design sensitivities) of the objective function and constraints with respect to the design variables. The DSA formulations are derived through chain-ruled derivatives using the finite element method (FEM) and BEM by using the direct differentiation and continuum variation concepts. The proposed approaches are implemented and validated using a numerical example.

An acoustic testing device composed of 2 probe microphones was developed for the electro-acoustic specification testing of the ITE (In-The-Ear) hearing aid (HA). The amplitude ratio and the phase difference between the incident pressure onto the HA microphone and the outward pressure of the HA receiver were measured by the present acoustic system. The microphones were particularly used because of small acoustic cavities where input and output pressures were present. The acoustic wall composed of clay completely blocks the propagation of the sound pressure between the small acoustic cavities. The system has an advantage of structural flexibility for the acoustic testing of different sizes and shapes of ITE-type HAs.

This paper proposed a MR(Magneto-rheological) seat damper for a commercial vehicle. After formulating the governing equation of motion, an appropriate size of damper is designed and manufactured. Following the equation of fie d-dependent damping force characteristics, a semi-active seat suspension installed with the proposed MR-damper is constructed and its dynamic model id established, Subsequently, vibration isolation performance of the semi-active suspension system is demonstrated by incorporating with a MRAC(Model referenced adaptive control) fer the MR Seat Damper

A Real Time Mode Selecting Stochastic Controller (RTMSSC) is developed as a new control strategy for a vibrating system under irregular disturbance. Displacement information and frequency characteristics obtained from me::id analysis of the system are used to design a Mode Selecting Controller. This Paper explains design technique of RTNSSC by applying it to the suppression of a flexible beam experiencing random vibration. The RTMSSC is designed by stochastic control from the modal information. The frequency information of the flexible system is utilized from the Mode Selecting Unit (MSU) based on a Fast-Fourier Transformation algorithm. The performance of the proposed technique, RTMSSC, is compared with that of Real Time Stochastic Controller developed recently, which show quite promising results.

This paper proposes a self-organizing fuzzy controller (SOFC) design technique applied to the vibration control of a dynamic system under irregular disturbance. In this controller, the fuzzy rules generate control signal continuously using the array of input and output pairs without using any special controller model. The generated rules are saved in the fuzzy rule matrix in real-time by self-organizing methods. This fuzzy logic control is demonstrated by simulation and shows the efficiency of the real-time self-organizing fuzzy controller in this system.

In this paper, Firstly, it is shown that the high vibration and noise source of piping and pump system is the acostic resonance. Secondly, in order to decrese the high vibration and noise of piping and pump system, the acostic mode of piping have been changed and its effectiveness is investigated as applied it at piping system practically.

In this paper, Firstly, it is shown that the high vibration source of piping system is the pulsation transmission of pipe line element ,such as, orifice plate, valves and the control valve is a broad band source and the branch wall and the cavity have vortex frequency Secondly, in order to decrese the turbulence vibration of piping system, the practical analysis of piping flow by EFD have been developed and its effectiveness is investigated as applying it at piping system practically.

This paper presents the vibration characteristics of a cantilever beam in contact with a fluid using a PZT actuator and PVDF film. dynamic behaviors of a flexible beam-water interaction system are examined. The effect of the liquid level on free vibration of the composite beam in a partially liquid-filled circular cylinder is investigated. The coupled system is subject to an undisturbed boundary condition un the fluid domain. In the vibration analysis of a wetted beam. the decoupled analyses between beam and fluid have been conventionally employed by considering first the composite beam vibration in the all and secondly Performing the correction taking account for surrounding fluid effects. That is, this investigation was to look at how natural frequencies, mode shapes. and damping are affected by liquid level variations. The signals from the sensor according to the applied input voltage are digitalized and filtered in order to obtain the dynamic characteristics of the composite beam in contact with fluid. It was found that the coupled natural frequencies decreased with the fluid level for the identical composite beam due to added mass effect. In case of the free-free boundary condition, the natural frequency gently decreased at fluid water level between 20% and 80% in the first tending mode and we found out the bends of stair shape for added mass effect of the fluid.

A liquid storage rectangular tank structures are used in many fields of civil, mechanical and marine engineering. Especially, Ship structures have many tanks in contact with inner or outer fluid, like ballast, fuel and cargo tanks. Fatigue damages are sometimes observed in these tanks which seem to be caused by resonance with exciting force of engine and propeller. Vibration characteristics of these thin walled tanks ill contact with fluid near engine or propeller are strongly affected by added mass of containing fluid. Therefore it is essentially important to estimate the added mass effect to predict vibration of the tank structures. In the previous report, we have developed numerical tool of vibration analysis of 3-dimensional tank structure using finite elements for plates and boundary elements for fluid region. In the present report, using the numerical analysis, vibrations characteristics in deep water tank are investigated and discussed.

An iterative modal analysis approach is developed to determine the effect of transverse open cracks on the dynamic behavior of simply supported Euler-Bernoulli beams with the moving masses. The influences of the velocities of moving masses, the distance between the moving masses and a crack have been studied on the dynamic behavior or a simply supported beam system by numerical method. no presence or crack results in large deflection of beam. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments i.e. the crack is modelled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces across the crack section and is derived by applying fundamental fracture mechanics theory. Totally, as the velocity of the moving masses and the distance between the moving masses are increased, the mid-span deflection of simply supported beam with the crack is decreased.

Flexure bearings have been used in linear-resonant compressors to maintain a non-contacting clearance seal between the piston and cylinder. There are two types of tangential cantilever bearing and spiral arm bearing with flexure bearings. A newly devised linear flexure bearing (KIMM-Ml) for compression refrigeration machines is disclosed having improved tight gas clearance maintaining capability for better system performance. KIMM-Ml is an integrated device comprising an axially moving diaphragm with circumferentially arranged arc-shaped flexure blades secured between rim and hub spacers, which turn out to have higher radial stiffness than the one with circumferential tangential cantilever flexure blades. It is expected for KIMM-Ml to play a key role in designing long life, special purpose compression refrigeration machines by providing frictionless, non-wearing, linear movement and radial support for the machines as well as a gas clearance seal by maintaining extremely tight clearances between piston and cylinder.

진동에 민감한 각종 정밀장비를 갖추고 있는 공장구조물은 설립하는 설계 초기단계에서부터 정밀장비가 정상 운용을 위하여 공장구조물의 진동허용규제치 및 동특성허용규제치를 결정해야 한다. 이를 만족할 수 있도록 공장구조물 설계시 진동측면에 대하여 동적 특성을 검토해야만 한다. 이때 반드시 필요한 자료로 정밀장비 Maker에게서 제공되는 진동허용규제치 및 구조물의 동특성허용규제치 등 설치시방의 상세한 자료를 제공받아야 한다 이러한 선계조건을 만족시켜주기 위한 방안으로 외부에서 정밀장비로 유입되는 진동에 대한 진동절연을 위하여 진동전달률 이론을 적용하여 방진효율 산출하는 방법과 정밀장비에서 발생하는 동하중을 고려하여 공장구조물에 대한 동적설계를 수행하는 것으로, 구조물 동특성을 요구되는 만큼 구조물 동특성 변경 SDM(Structural Dynamic Modifacation)방법이 주로 활용된다. 이에 본 연구에서는 앞서 언급한 구조물의 동적설계시 후자조건인 구조물의 동특성을 변경하고자 하는 경우에 실구조물에 하중을 정량적으로 조절하며 가할 수 있는 VSD 시스템을 이용하여 구조물의 동특성을 변화시키는 것을 동적해석으로 예측하였고, 현장에서 실제 동적실험으로 구한 결과를 동적설계 목표치와 비교하여 유용성에 대하여 확인하였다.

In this thesis, the dynamic characteristic analysis of carriage structure supported by air bearings were peformed. Toward this end, the characteristics of air bearing were numerically analyzed to estimate the stiffness of the air bearing and the clearance between air bearing and guide surface. The modal analysis of the carriage structure was peformed by using finite element method, and the experimental modal analysis was also performed to validate the finite element model, where rigid body modes were compared to validate the stiffness of the air bearings. From the results, the air spring stiffness can be estimated within the range of acceptable accuracy under any pressure and clearance condition.

The vibration isolation table system for the high precision Processing machinery has been developed. The system uses air spring as its isolation elements. An investigation of the model and the test results showed that the diaphragm has a role in the mathematical model. The vibration levels at various floors in the laboratory were investigated during operating the large shaking table for the selection of optimum installation location. The vibration test on the designed system showed good isolation performances.

For many years, engineers in the field of acoustics have used the A-weighted sound pressure level (SPL). Since they were interested just in a reduction of noise, the A-weighted SPL was considered good enough to quantify noise problems. This is reasonable because loudness is usually the most important parameter for most noise problems and A-weighted SPL is often reasonably well correlated with loudness. As the overall noise levels drop, however, other parameters become more important and must be considered, Advent of sound quality came from an understanding that A-weighted SPL only reflects the loudness of a sound. It is obviously impossible to characterize a complex sound with a single number. Although product mostly has revealed physical quantities created by the standpoint of engineers, consumers perceive and evaluate products on the non-physical characteristics, such as feelings, emotions, and experiences in different social and cultural situations. Especially, for the household appliances for instance air-conditioner or refrigerator, the sound is heavily related to the satisfaction of a customer who is a real user of the product and is very important factor to decide purchasing as well as visual design. Therefore, in this research, the general tendency of consumer's psychology was investigated for the appliances. And also, in order to obtain clear guidelines fur sound manipulation, the characteristics of the sound of air-conditioning systems and refrigerators were compared with competitors'. since it is important to overcome the discrepancy between engineering and marketing, the relevance of sound manipulation must be documented from the consumer's perspective. That is the reason why we conducted a consumer and marketing oriented study.

A gas driven heat pump (GHP) core design comprises internal combustion engine, compressors incorporated to a cooling/heating system, rubber mountings and belt transmissions. Main excitation farces are generated by an engine, compressors themselves and belt fluctuation. It leads to high vibration level of the mount that can cause damage of GHP elements. Therefore an appropriate design of the mounting system is crucial in terms of reliability and vibration reduction. In this paper oscillation of the engine mount is explored both experimentally and analytically. Experimental analysis of natural frequencies and operational frequency response of the GHP engine mounting system enables to create simplified model for numerical and analytical investigations. It is worked out criteria f3r vibration abatement of the isolated structure. Influence of bracket stiffness between engine and compressors, suspension locations and damper performance is investigated. Ways to reduce excitation forces and improve dynamic performance of the engine-compressor mounting system are considered from these analyses. Implementation of the proposed approach permits to choose appropriate rubber mountings and their location as well as joining elements design A phase matching technique can be employed to control forces from main exciters. It enables to changing vibration response of the structure by control of natural modes contribution. Proposed changes lead to significant vibration reduction and can be easily utilized in engineering practice.

Vibration problems are an intrinsic characteristic in a washing machine owing to rotation working mechanism. Therefore, a right comprehension of working principle and the analysis on dynamic behavior of a washing machine is essential to design anti-vibration or vibration reduction. In this paper, we choose two kinds of a washing machine: a suspension type pulsator/drum type washing machine. Each the structure and working principle of a washing machine is discussed briefly and the dynamic behavior of it is investigated, then, the vibration detection problems of transient or excessive vibration is tented in each category. Some vibration experimented results in a washing machine are presented also.

In this paper, some dominant aeroacoustic characteristics of fans used in appliances are reviewed. The numerical attempts to analyze tile aeroacoustic noise of fans are briefly reviewed for various fans. Axial fans for refrigerator, cross flow fans fer air-conditioner, sirocco fans and turbo fans are anal: zed. The unsteady flow field, which is essential data for aeroacoustic analysis, is calculated by commercial CFD code. Acoustic pressure is calculated by Ffowcs Williams and Hawkings equation and Lowson's equation. During the analysis, dominant noise sources are identified.

So far the study of near-field optical recording(NFR) suspensions has not been investigated sufficiently. In this study the optimization of a NFR suspension is performed using finite element method. NFR suspensions are required to have low compliance modes to allow the slider to comply with the rotating disk, and high tracking stiffness modes to maximize the servo bandwidth of the tracking controller First of all, a basic integrated type suspension model is obtained using topology optimization And the parametric study on the sensitivities of the compliance modes and tracking stiffness modes is performed. Finally, a model satisfying static characteristics is elected and shape optimization is performed to improve dynamic characteristics.

Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. PIV measurement was used fer the unsteady flow between the center pair of four disks of four times larger than common radius of HDD disk at several rpm in a fixed cylindrical enclosure. The boundary between inner region and outer region is detected using PIV measurement and the number of dominant vortices s determined clearly. Tip vortices generated by an obstruction with actual-like configuration can be found at inner region. Oscillating flow from the obstruction appears at outer region with complex flow pattern.

Dynamic Load/unload (L/UL) mechanism is an alternative to the contact start stop (CSS) technology which eliminates stiction and wear failure modes associated with CSS. Other benefits of L/UL include increased areal density due to smooth disk surfaces, thinner overcoats, and lower head flying height Improved shock resistance due to elimination of head slap, and reduced power consumption. Inertia latch mechanism becomes important for mobile disk drives because of non operating shock performance. Various types of latch designs have been introduced in hard disk drives to limit a rotary actuator from sudden uncontrolled motion. In this paper, a single spring inertia latch is introduced for a small form optical disk drive, which uses a rotary actuator for moving an optical pick-up. A new small inertia latch with single spring is designed to ensure both feasible and small size. The shock performance of the new inertia latch is experimentally verified.

This paper presents an approach to optimally design the air-bearing surface (ABS) of the optical flying head for near-field recording technology (NFR). NFR is an optical recording technology using very small beam spot size by overcoming the limit of beam diffraction. One of the most Important problems in NFR is a head disk interface (HDI) issue over the recording band during the operation. A multi-criteria optimization problem is formulated to enhance the flying performances over the entire recording band during the steady state. The optimal solution of the slider, whose target flying height is 50 nm, is automatically obtained. The flying height during the steady state operation becomes closer to the target values than those fur the initial one. The pitch and roll angles are also kept within suitable ranges over the recording band. Especially, all of the air-bearing stiffness are drastically increased by the optimized geometry of the air bearing surface.

Recently, the disturbance caused by an optical disk vibration and the external vibration/shock are more serious problem in an optical disk drives (ODD) as an ODD become small size and rotation speed increases. The conventional controller cannot cope with the mentioned problems properly when the disturbance and vibration are larger than some range. Therefore, we propose a new control scheme using a disturbance observer (DOB) and it can control the aforementioned problems. The designed the controller is applied to a commercial ODD in focusing direction, then its validity is proved by experimental method. By rising the disturbance observer theory, the focusing performance is conspicuously improved in the presence of sinusoidal vibrations or a shock disturbance. This algorithm also applies to a tracking structure also, because focusing structure is very similar to it.

As the delay of the Kyungbu High Speed Railroad, HST should use conventional line through Daegoo to Pusan until the new railroad build. High speed railroad noise is one of the main causes of environmental impact. Whenever HST on conventional railroad line is planned or HST service into the urban center is proposed, an estimate of the relevant noise levels is usually required. For this, it is necessary to quantify those parameters that affect the railroad noise. This paper deals with an estimation of high speed railroad noise in urban center.

Noise map is becoming an increasingly important tool supporting noise policy. In order to main am a quiet environment of urban areas, noise map was developed by using GIS technique which combines geographic and noise informations with a database management system. By evaluating various methods of the spatial anal: sis, it was concluded that the inverse distance weighted method gave the best results and was applied to develope the noise maps of road noise.

The railroad noise has been considered as one of environment pollution and complaints about it have been increasing every you. Therefore, the establishment of railroad noise monitoring network is necessary. It will be designed for monitoring railroad noise, storing data of railroad noise continuously and providing the fundamental knowledge for the measures of railroad noise. For this, we investigated the actual condition of railroad noise and status of noise level by floor in apartments around the capital region, Daejeon, Daegu, Gwangju, and Busan. Additionally, we present the basic data that will be used for predicting the noise level near railroad in the environmental impact assessment

Noise reduction effect of a pine tree which was used to reinforce a noise barrier was studied by using reduced scale model test. The result show that the pine tree itself was less effective but the combination of pine tree and noise barrier was good for reducing the noise and sight.

Urban subways usually make environmental problems because subway vibrations are transmitted to building structures. However, when the buildings are designed, vibrations due to subway are not usually considered in advance. This results in many environmental vibration problems after buildings are constructed. This study was carried out to set up and evaluate a pre-assessment technique for the environmental impact of urban subway vibration on newly planned buildings near a subway line. for this purpose, semi-emperical method was set up and vibration measurements were made on site in accordance with construction schedule. Computer simulation was also performed using ANSYS software to predict the building vibration and compared with the measured results for evaluation of the pre-assessment technique.

An unconstrained tuning fork with a 3-D model has been numerically analyzed by Finite Element Method(FEM) and Boundary Element Method (BEM). The first three natural frequencies were calculated by the FEM modal analysis. Then the trend of the change of the modal frequencies was examined with the variation of the tuning fork length and width. An formula for the natural frequencies-tuning fork length relationship were derived from the numerical analysis results. Finally the BEM was used fur the sound pressure field calculation from the structural displacement data.

Rotary compressors are one of the most important parts of air-conditioners in the industry This device usually has noise problems during the circulation process of the refrigerant and muffler is used for the noise reduction. The acoustic performance of the muffler depends on its shape and its hole locations on the upper surface. Therefore finding the optimum location of the muffler holes is a topic of increasing importance in the compressor industry. In this research the optimization of the muffler hole locations and the importance of the resonator cavity on the lower surface of the muffler in acoustic point of view is studied. At first, the topology optimization for the 2 hole muffler is performed based on a model without resonator cavity by using genetic algorithm. The 2 hole muffler's acoustic analysis and experiment results are matching, however, the optimized model's results are not. By adding the resonator cavity and also by changing the cavity shape, the acoustic analysis and experiment result comparison is Performed for different cavity shapes. The topology optimization of the revised model with cavity is carried out for noise reduction. Finally, the optimized design is produced and tested for validation.

Shell vibrations of the rotary compressor, which account for considerable portion of the noise from compressor, are caused by various sources. Among them is the vibration of the in nor part or cylinder assembly, which undergoes severe compression process and rotational motion. But little researches have been carried out about the behavior and effect of the inner part because of its structural complexity. Furthermore, the shell of the rotary compressor is hermetic type that experimental approach is very difficult. This research studied the structure-born noise of the Rotary compressor using FE an analysis. The comparison between sound pressure spectrum and natural frequencies of the shell vibration implies that shell vibrations contribute significantly to the noise. It is found that inner part vibrations are responsible for those through the FE analysis. Design modification of the inner part, which shifts the target frequencies, reduced overall noise level of the compressor.